diff --git a/app/Models/Foundation/Summit/ScheduleEntity.php b/app/Models/Foundation/Summit/ScheduleEntity.php
index 7d735a848..867b9578e 100644
--- a/app/Models/Foundation/Summit/ScheduleEntity.php
+++ b/app/Models/Foundation/Summit/ScheduleEntity.php
@@ -70,23 +70,39 @@ private function _getSummitId(): int
     #[ORM\PreRemove]
     public function deleting($args)
     {
-        Event::dispatch(new ScheduleEntityLifeCycleEvent(ScheduleEntityLifeCycleEvent::Operation_Delete,
-            $this->_getSummitId(),
-            $this->id,
-            $this->_getClassName()));
+        try {
+            Event::dispatch(new ScheduleEntityLifeCycleEvent(ScheduleEntityLifeCycleEvent::Operation_Delete,
+                $this->_getSummitId(),
+                $this->id,
+                $this->_getClassName()));
+        } catch (\Exception $ex) {
+            // Lifecycle notifications must not abort Doctrine transactions.
+            // A queue/cache failure here should never roll back the delete.
+            Log::warning(sprintf(
+                "ScheduleEntity::deleting failed to dispatch lifecycle event for %s id %s: %s",
+                $this->_getClassName(), $this->id, $ex->getMessage()
+            ));
+        }
     }
 
     #[ORM\PostRemove]
     public function deleted($args)
     {
-        $this->cachedDeleted($args);
+        try {
+            $this->cachedDeleted($args);
+        } catch (\Exception $ex) {
+            Log::warning(sprintf(
+                "ScheduleEntity::deleted failed cache cleanup for %s id %s: %s",
+                $this->_getClassName(), $this->id, $ex->getMessage()
+            ));
+        }
     }
 
     #[ORM\PreUpdate]
     public function updating(PreUpdateEventArgs $args)
     {
         parent::updating($args);
-    }
+     }
 
     #[ORM\PostUpdate]
     public function updated($args)
@@ -94,22 +110,43 @@ public function updated($args)
         if($this->shouldSkipDataUpdate()){
             Log::debug(sprintf("ScheduleEntity::updated skipping data update for id %s type %s ...", $this->id, $this->_getClassName()));
             return;
-        };
+        }
         Log::debug(sprintf("ScheduleEntity::updated id %s", $this->id));
-        $this->cachedUpdated($args);
-        Event::dispatch(new ScheduleEntityLifeCycleEvent(ScheduleEntityLifeCycleEvent::Operation_Update,
-            $this->_getSummitId(),
-            $this->id,
-            $this->_getClassName()));
+        try {
+            $this->cachedUpdated($args);
+        } catch (\Exception $ex) {
+            Log::warning(sprintf(
+                "ScheduleEntity::updated failed cache update for %s id %s: %s",
+                $this->_getClassName(), $this->id, $ex->getMessage()
+            ));
+        }
+        try {
+            Event::dispatch(new ScheduleEntityLifeCycleEvent(ScheduleEntityLifeCycleEvent::Operation_Update,
+                $this->_getSummitId(),
+                $this->id,
+                $this->_getClassName()));
+        } catch (\Exception $ex) {
+            Log::warning(sprintf(
+                "ScheduleEntity::updated failed to dispatch lifecycle event for %s id %s: %s",
+                $this->_getClassName(), $this->id, $ex->getMessage()
+            ));
+        }
     }
 
     // events
     #[ORM\PostPersist]
     public function inserted($args)
     {
-        Event::dispatch(new ScheduleEntityLifeCycleEvent(ScheduleEntityLifeCycleEvent::Operation_Insert,
-            $this->_getSummitId(),
-            $this->id,
-            $this->_getClassName()));
+        try {
+            Event::dispatch(new ScheduleEntityLifeCycleEvent(ScheduleEntityLifeCycleEvent::Operation_Insert,
+                $this->_getSummitId(),
+                $this->id,
+                $this->_getClassName()));
+        } catch (\Exception $ex) {
+            Log::warning(sprintf(
+                "ScheduleEntity::inserted failed to dispatch lifecycle event for %s id %s: %s",
+                $this->_getClassName(), $this->id, $ex->getMessage()
+            ));
+        }
     }
 }
diff --git a/app/Models/OAuth2/ResourceServerContext.php b/app/Models/OAuth2/ResourceServerContext.php
index bfc46a25d..a853fe400 100644
--- a/app/Models/OAuth2/ResourceServerContext.php
+++ b/app/Models/OAuth2/ResourceServerContext.php
@@ -249,6 +249,16 @@ public function getCurrentUser(bool $synch_groups = true, bool $update_member_fi
                 // update member fields
                 if (!empty($user_email)) {
                     Log::debug(sprintf("ResourceServerContext::getCurrentUser setting email for member %s", $member->getId()));
+                    // guard against email collision: another member may already hold this email
+                    $member_by_email = $this->member_repository->getByEmail($user_email);
+                    if (!is_null($member_by_email) && $member_by_email->getId() !== $member->getId()) {
+                        Log::warning(sprintf(
+                            "ResourceServerContext::getCurrentUser email %s already owned by member %s, invalidating it",
+                            $user_email,
+                            $member_by_email->getId()
+                        ));
+                        $member_by_email->setEmail(sprintf("%s-invalid@invalid", $member_by_email->getId()));
+                    }
                     $member->setEmail($user_email);
                 }
 
diff --git a/app/Providers/EventServiceProvider.php b/app/Providers/EventServiceProvider.php
index 68641c68a..862c6bacd 100644
--- a/app/Providers/EventServiceProvider.php
+++ b/app/Providers/EventServiceProvider.php
@@ -348,13 +348,15 @@ public function boot()
 
             Log::debug(sprintf("ScheduleEntityLifeCycleEvent event %s", $event));
 
-            ProcessScheduleEntityLifeCycleEvent::dispatch
-            (
-                $event->entity_operator,
-                $event->summit_id,
-                $event->entity_id,
-                $event->entity_type,
-                $event->params
+            JobDispatcher::withDbFallback(
+                new ProcessScheduleEntityLifeCycleEvent(
+                    $event->entity_operator,
+                    $event->summit_id,
+                    $event->entity_id,
+                    $event->entity_type,
+                    $event->params
+                ),
+                ['entity_type' => $event->entity_type, 'entity_id' => $event->entity_id]
             );
         });
 
diff --git a/app/Services/Model/Imp/MemberService.php b/app/Services/Model/Imp/MemberService.php
index 4c3955973..34b2a92d9 100644
--- a/app/Services/Model/Imp/MemberService.php
+++ b/app/Services/Model/Imp/MemberService.php
@@ -316,6 +316,14 @@ public function registerExternalUser(ExternalUserDTO $userDTO): Member
             );
             $member = $this->member_repository->getByExternalIdExclusiveLock($userDTO->getId());
             if(is_null($member)) {
+                // guard against email collision: a former member (e.g. a failed delete) may still hold this email
+                $member_by_email = $this->member_repository->getByEmail($userDTO->getEmail());
+                if(!is_null($member_by_email) && $member_by_email->getUserExternalId() != $userDTO->getId()) {
+                    // the idp is the source of truth
+                    Log::warning(sprintf("MemberService::registerExternalUser there is a former user with same email %s former id %s invalidating email", $userDTO->getEmail(), $member_by_email->getId()));
+                    $member_by_email->setEmail(sprintf("%s-invalid@invalid", $member_by_email->getUserExternalId()));
+                    $this->member_repository->add($member_by_email, true);
+                }
                 $member = new Member();
                 $member->setUserExternalId($userDTO->getId());
                 $member->setActive($userDTO->isActive());
@@ -342,11 +350,20 @@ public function registerExternalUserByPayload(array $user_data):Member{
         // first by external id due email could be updated
         Log::debug(sprintf("MemberService::registerExternalUserByPayload trying to get user by external id %s", $user_external_id));
         $member = $this->member_repository->getByExternalIdExclusiveLock(intval($user_external_id));
+        $member_by_email = $this->member_repository->getByEmail($email);
+        // if there are 2 users and the email was transferred to the new external id
+        if(!is_null($member) && !is_null($member_by_email) && $member_by_email->getUserExternalId() != $user_external_id) {
+          // the idp is the source of truth
+            Log::warning(sprintf("MemberService::registerExternalUserByPayload there is a former user with same email %s former id %s invalidating email", $email, $member_by_email->getId()));
+            $member_by_email->setEmail(sprintf("%s-invalid@invalid", $member_by_email->getUserExternalId()));
+            $this->member_repository->add($member_by_email, true);
+        }
         // if we dont registered yet a member with that external id try to get by email
         if(is_null($member)) {
             Log::debug(sprintf("MemberService::registerExternalUserByPayload trying to get user by email %s", $email));
-            $member = $this->member_repository->getByEmail($email);
+            $member = $member_by_email;
         }
+
         $is_new = false;
         if(is_null($member)) {
             Log::debug(sprintf("MemberService::registerExternalUserByPayload %s does not exists , creating it ...", $email));
diff --git a/tests/MemberServiceTest.php b/tests/MemberServiceTest.php
new file mode 100644
index 000000000..d92773688
--- /dev/null
+++ b/tests/MemberServiceTest.php
@@ -0,0 +1,207 @@
+<?php namespace Tests;
+/**
+ * Copyright 2026 OpenStack Foundation
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * http://www.apache.org/licenses/LICENSE-2.0
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ **/
+use App\Services\Model\dto\ExternalUserDTO;
+use App\Services\Model\IMemberService;
+use Illuminate\Support\Facades\App;
+use Illuminate\Support\Facades\DB;
+use LaravelDoctrine\ORM\Facades\EntityManager;
+use LaravelDoctrine\ORM\Facades\Registry;
+use libs\utils\ITransactionService;
+use models\main\Member;
+use models\utils\SilverstripeBaseModel;
+
+/**
+ * Class MemberServiceTest
+ *
+ * Reproduces S3213: when the IDP deletes a user account and reassigns its email
+ * to a different external id, registering the new external id must free the old
+ * member's email (the IDP is the source of truth) instead of failing on the
+ * unique email constraint.
+ */
+final class MemberServiceTest extends TestCase
+{
+    /** @var \Doctrine\ORM\EntityManagerInterface */
+    private $em;
+
+    /** @var \Doctrine\Persistence\ObjectRepository */
+    private $member_repository;
+
+    /** @var int */
+    private $old_external_id;
+
+    /** @var int */
+    private $new_external_id;
+
+    /** @var int */
+    private $create_external_id;
+
+    /** @var string */
+    private $reassigned_email;
+
+    protected function setUp(): void
+    {
+        parent::setUp();
+
+        DB::setDefaultConnection("model");
+
+        $this->em = Registry::getManager(SilverstripeBaseModel::EntityManager);
+        if (!$this->em->isOpen()) {
+            $this->em = Registry::resetManager(SilverstripeBaseModel::EntityManager);
+        }
+        $this->member_repository = EntityManager::getRepository(Member::class);
+
+        $prefix = str_random(10);
+        // emails are normalized to lowercase by the repository lookups
+        $this->reassigned_email = strtolower("reassign+{$prefix}@test.com");
+        // ExternalUserId is a signed INT column (max 2147483647); keep ids in range and non-overlapping
+        $this->old_external_id    = mt_rand(1000000000, 1299999999);
+        $this->new_external_id    = mt_rand(1300000000, 1599999999);
+        $this->create_external_id = mt_rand(1600000000, 1999999999);
+
+        // member that currently owns the email, tied to the old (deleted) external id
+        $old_member = new Member();
+        $old_member->setEmail($this->reassigned_email);
+        $old_member->setActive(true);
+        $old_member->setEmailVerified(true);
+        $old_member->setFirstName("Old");
+        $old_member->setLastName("Owner");
+        $old_member->setUserExternalId($this->old_external_id);
+
+        // member already provisioned for the new external id, with a different email
+        $new_member = new Member();
+        $new_member->setEmail(strtolower("new+{$prefix}@test.com"));
+        $new_member->setActive(true);
+        $new_member->setEmailVerified(true);
+        $new_member->setFirstName("New");
+        $new_member->setLastName("Owner");
+        $new_member->setUserExternalId($this->new_external_id);
+
+        $this->em->persist($old_member);
+        $this->em->persist($new_member);
+        $this->em->flush();
+    }
+
+    protected function tearDown(): void
+    {
+        try {
+            if (!$this->em->isOpen()) {
+                $this->em = Registry::resetManager(SilverstripeBaseModel::EntityManager);
+            }
+            foreach ([$this->old_external_id, $this->new_external_id, $this->create_external_id] as $external_id) {
+                $member = $this->member_repository->findOneBy(['user_external_id' => $external_id]);
+                if (!is_null($member)) {
+                    $this->em->remove($member);
+                }
+            }
+            $this->em->flush();
+        } catch (\Exception $ex) {
+            // best-effort cleanup
+        }
+        parent::tearDown();
+    }
+
+    /**
+     * The IDP moved $reassigned_email from $old_external_id to $new_external_id.
+     * Registering the new external id with that email must:
+     *  - invalidate the old member's email (so the unique constraint is freed), and
+     *  - assign the reassigned email to the member of the new external id.
+     * Before the fix this throws a unique-constraint violation on flush.
+     */
+    public function testRegisterExternalUserByPayloadReassignsEmailFromDeletedExternalId(): void
+    {
+        $payload = $this->buildExternalProfilePayload($this->new_external_id, $this->reassigned_email);
+
+        $tx_service = App::make(ITransactionService::class);
+        // mirror registerExternalUserById(): the pessimistic lock requires a transaction
+        $tx_service->transaction(function () use ($payload) {
+            return App::make(IMemberService::class)->registerExternalUserByPayload($payload);
+        });
+
+        $this->em->clear();
+
+        $owner_of_email = $this->member_repository->findOneBy(['email' => $this->reassigned_email]);
+        $this->assertNotNull($owner_of_email, "reassigned email should still belong to a member");
+        $this->assertEquals(
+            $this->new_external_id,
+            $owner_of_email->getUserExternalId(),
+            "reassigned email must now belong to the new external id"
+        );
+
+        $old_member = $this->member_repository->findOneBy(['user_external_id' => $this->old_external_id]);
+        $this->assertNotNull($old_member, "old member must still exist");
+        $this->assertEquals(
+            sprintf("%s-invalid@invalid", $this->old_external_id),
+            $old_member->getEmail(),
+            "old member's email must be invalidated"
+        );
+    }
+
+    /**
+     * Creating a brand-new external user whose email is still held by a former member
+     * (e.g. a member whose delete failed) must invalidate the former member's email
+     * instead of failing on the Member.Email unique constraint.
+     */
+    public function testRegisterExternalUserInvalidatesFormerMemberEmailOnCreate(): void
+    {
+        $dto = new ExternalUserDTO(
+            $this->create_external_id,
+            $this->reassigned_email,
+            'Created',
+            'User',
+            true,
+            true
+        );
+
+        App::make(IMemberService::class)->registerExternalUser($dto);
+
+        $this->em->clear();
+
+        $owner_of_email = $this->member_repository->findOneBy(['email' => $this->reassigned_email]);
+        $this->assertNotNull($owner_of_email, "reassigned email should belong to a member");
+        $this->assertEquals(
+            $this->create_external_id,
+            $owner_of_email->getUserExternalId(),
+            "reassigned email must now belong to the newly created external id"
+        );
+
+        $former_member = $this->member_repository->findOneBy(['user_external_id' => $this->old_external_id]);
+        $this->assertNotNull($former_member, "former member must still exist");
+        $this->assertEquals(
+            sprintf("%s-invalid@invalid", $this->old_external_id),
+            $former_member->getEmail(),
+            "former member's email must be invalidated"
+        );
+    }
+
+    private function buildExternalProfilePayload(int $external_id, string $email): array
+    {
+        return [
+            'id'                                       => $external_id,
+            'email'                                    => $email,
+            'active'                                   => true,
+            'email_verified'                           => true,
+            'first_name'                               => 'Reassigned',
+            'last_name'                                => 'User',
+            'bio'                                      => '',
+            'groups'                                   => [],
+            'public_profile_show_photo'                => false,
+            'public_profile_show_fullname'             => false,
+            'public_profile_show_email'                => false,
+            'public_profile_show_telephone_number'     => false,
+            'public_profile_show_bio'                  => false,
+            'public_profile_show_social_media_info'    => false,
+            'public_profile_allow_chat_with_me'        => false,
+        ];
+    }
+}