Bug: Cannot confirm/create meeting from accepted Talk Meeting Proposal — error on confirmation

[GretaD]

Steps to reproduce

1. Open Nextcloud Calendar → create a Meeting Proposal (Appointment slots / poll).
2. Share the proposal link with participants.
3. Participants vote for one or more available time slots.
4. Organizer opens the proposal results and tries to confirm a time slot / create the meeting.
5. Observe: an error is shown and the meeting is not created.

Expected behavior

Meeting is created

Actual behavior

I get an error instead

Calendar app version

6.2.0

CalDAV-clients used

No response

Browser

all of them

Client operating system

No response

Server operating system

No response

Web server

None

Database engine version

None

PHP engine version

None

Nextcloud version

No response

Updated from an older installed version or fresh install

None

List of activated apps

Nextcloud configuration

Web server error log

Log file

{"reqId":"In5VpjmyaejjwpES0Ec3","level":3,"time":"2026-03-09T10:52:03+00:00","remoteAddr":"192.168.21.4","user":"admin","app":"no app in context","method":"POST","url":"/ocs/v2.php/calendar/proposal/convert","scriptName":"/ocs/v2.php","message":"An exception occurred while executing a query: SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '1-0-0e4f784c-e693-472c-8bfb-40374ec8e678' for key 'calobjects_by_uid_index'","userAgent":"Mozilla/5.0 (X11; Linux x86_64; rv:148.0) Gecko/20100101 Firefox/148.0","version":"32.0.6.1","exception":{"Exception":"OC\\DB\\Exceptions\\DbalException","Message":"An exception occurred while executing a query: SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '1-0-0e4f784c-e693-472c-8bfb-40374ec8e678' for key 'calobjects_by_uid_index'","Code":1062,"Trace":[{"file":"/var/www/html/lib/private/DB/ConnectionAdapter.php","line":69,"function":"wrap","class":"OC\\DB\\Exceptions\\DbalException","type":"::","args":[{"__class__":"Doctrine\\DBAL\\Exception\\UniqueConstraintViolationException"},"","INSERT INTO `*PREFIX*calendarobjects` (`calendarid`, `uri`, `calendardata`, `lastmodified`, `etag`, `size`, `componenttype`, `firstoccurence`, `lastoccurence`, `classification`, `uid`, `calendartype`) VALUES(:dcValue1, :dcValue2, :dcValue3, :dcValue4, :dcValue5, :dcValue6, :dcValue7, :dcValue8, :dcValue9, :dcValue10, :dcValue11, :dcValue12)"]},{"file":"/var/www/html/lib/private/DB/QueryBuilder/QueryBuilder.php","line":308,"function":"executeStatement","class":"OC\\DB\\ConnectionAdapter","type":"->","args":["INSERT INTO `*PREFIX*calendarobjects` (`calendarid`, `uri`, `calendardata`, `lastmodified`, `etag`, `size`, `componenttype`, `firstoccurence`, `lastoccurence`, `classification`, `uid`, `calendartype`) VALUES(:dcValue1, :dcValue2, :dcValue3, :dcValue4, :dcValue5, :dcValue6, :dcValue7, :dcValue8, :dcValue9, :dcValue10, :dcValue11, :dcValue12)",{"dcValue1":"*** sensitive parameters replaced ***","dcValue2":"*** sensitive parameters replaced ***","dcValue3":"*** sensitive parameters replaced ***","dcValue4":1773053523,"dcValue5":"45ec6a55aaa58da1e56e8d22047ffadb","0":"And 7 more entries, set log level to debug to see all entries"},{"dcValue1":2,"dcValue2":2,"dcValue3":3,"dcValue4":2,"dcValue5":2,"0":"And 7 more entries, set log level to debug to see all entries"}]},

Browser log

Additional info

No response

[GVodyanov]

Here is a screenshot of it happening

status 500 on ocs/v2.php/calendar/proposal/convert

{
   "ocs":{
      "meta":{
         "status":"failure",
         "statuscode":996,
         "message":"Internal Server Error\nAn exception occurred while executing a query: SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '1-0-cfc2d6f5-17f0-4eec-a715-7898a5fc9e0a' for key 'calobjects_by_uid_index'"
      },
      "data":[
         
      ]
   }
}