diff --git a/UI/FleetWnd.cpp b/UI/FleetWnd.cpp
index 18c490df964..99d346477e1 100644
--- a/UI/FleetWnd.cpp
+++ b/UI/FleetWnd.cpp
@@ -1700,52 +1700,94 @@ class FleetsListBox : public CUIListBox {
     }
 
     virtual void    AcceptDrops(const std::vector<GG::Wnd*>& wnds, const GG::Pt& pt) {
-        //std::cout << "FleetsListBox::AcceptDrops" << std::endl;
-        assert(!wnds.empty());
+        DebugLogger() << "FleetsListBox::AcceptDrops";
+        if (wnds.empty()) {
+            ErrorLogger() << "... dropped wnds empty";
+            return;
+        }
+        if (!m_order_issuing_enabled) {
+            DebugLogger() << "... order issuing disabled, aborting";
+            return;
+        }
+
+
 
         iterator drop_target_row = RowUnderPt(pt);
-        assert(m_order_issuing_enabled && drop_target_row != end());
+        DebugLogger() << "... drop pt: " << pt;
+        if (drop_target_row == end()) {
+            DebugLogger() << "... drop row is end, aborting";
+            return;
+        }
+        DebugLogger() << "... drop row is in position: " << std::distance(begin(), drop_target_row);
 
 
         // get drop target fleet
         const FleetRow* drop_target_fleet_row = boost::polymorphic_downcast<FleetRow*>(*drop_target_row);
-        assert(drop_target_fleet_row);
-
-        TemporaryPtr<Fleet> target_fleet = GetFleet(drop_target_fleet_row->FleetID());
-        assert(target_fleet);
+        if (!drop_target_fleet_row) {
+            ErrorLogger() << "... drop target not a fleet row. aborting";
+            return;
+        }
 
-        int target_fleet_id = target_fleet->ID();
+        int target_fleet_id = drop_target_fleet_row->FleetID();
+        TemporaryPtr<Fleet> target_fleet = GetFleet(target_fleet_id);
+        if (!target_fleet) {
+            ErrorLogger() << "... unable to get target fleet with id: " << target_fleet_id;
+            return;
+        }
 
 
         // sort dropped Wnds to extract fleets or ships dropped.  (should only be one or the other in a given drop)
         std::vector<TemporaryPtr<Fleet> > dropped_fleets;
         std::vector<TemporaryPtr<Ship> > dropped_ships;
 
+        DebugLogger() << "... getting/sorting dropped fleets or ships...";
         for (std::vector<Wnd*>::const_iterator it = wnds.begin(); it != wnds.end(); ++it) {
             const GG::Wnd* wnd = *it;
 
+            if (drop_target_fleet_row == wnd) {
+                ErrorLogger() << "... ... dropped wnd is same as drop target?! skipping";
+                continue;
+            }
+
             if (wnd->DragDropDataType() == FLEET_DROP_TYPE_STRING) {
                 const FleetRow* fleet_row = boost::polymorphic_downcast<const FleetRow*>(wnd);
-                assert(fleet_row);
+                if (!fleet_row) {
+                    ErrorLogger() << "... ... unable to get fleet row from dropped wnd";
+                    continue;
+                }
                 dropped_fleets.push_back(GetFleet(fleet_row->FleetID()));
 
             } else if (wnd->DragDropDataType() == SHIP_DROP_TYPE_STRING) {
                 const ShipRow* ship_row = boost::polymorphic_downcast<const ShipRow*>(wnd);
-                assert(ship_row);
+                if (!ship_row) {
+                    ErrorLogger() << "... ... unable to get ship row from dropped wnd";
+                    continue;
+                }
                 dropped_ships.push_back(GetShip(ship_row->ShipID()));
             }
         }
 
-        assert(dropped_ships.empty() != dropped_fleets.empty());    // should only be dropping fleets or ships, not a mix of both
+        if (dropped_ships.empty() && dropped_fleets.empty()) {
+            ErrorLogger() << "... no ships or fleets dropped... aborting";
+            return;
+        }
+
+        if (dropped_ships.empty() == dropped_fleets.empty()) {
+            ErrorLogger() << "... dropped a mix of fleets and ships... aborting";
+            return;
+        }
         int empire_id = HumanClientApp::GetApp()->EmpireID();
 
         if (!dropped_fleets.empty()) {
+            DebugLogger() << " ... processing dropped " << dropped_fleets.size() << " fleets";
             // dropping fleets.  get each ships of all source fleets and transfer to the target fleet
-            //std::cout << ".... dropped " << dropped_fleets.size() << " fleets" << std::endl;
 
             for (std::vector<TemporaryPtr<Fleet> >::const_iterator it = dropped_fleets.begin(); it != dropped_fleets.end(); ++it) {
                 TemporaryPtr<const Fleet> dropped_fleet = *it;
-                assert(dropped_fleet);
+                if (!dropped_fleet) {
+                    ErrorLogger() << "... ... unable to get dropped fleet?";
+                    continue;
+                }
                 int dropped_fleet_id = dropped_fleet->ID();
 
                 // get fleet's ships in a vector, as this is what FleetTransferOrder takes
@@ -1767,8 +1809,8 @@ class FleetsListBox : public CUIListBox {
             }
 
         } else if (!dropped_ships.empty()) {
+            DebugLogger() << " ... processing dropped " << dropped_ships.size() << " ships";
             // dropping ships.  transfer to target fleet.
-            //std::cout << ".... dropped " << dropped_ships.size() << " ships" << std::endl;
 
             // get source fleet of ship(s).  assumes all ships are from the same source fleet.
             TemporaryPtr<const Ship> first_ship = dropped_ships[0];
@@ -1779,7 +1821,10 @@ class FleetsListBox : public CUIListBox {
             std::set<int> dropped_ships_fleets;
             for (std::vector<TemporaryPtr<Ship> >::const_iterator it = dropped_ships.begin(); it != dropped_ships.end(); ++it) {
                 TemporaryPtr<const Ship> ship = *it;
-                assert(ship);
+                if (!ship) {
+                    ErrorLogger() << "... ... couldn't get dropped ship?";
+                    continue;
+                }
                 ship_ids_vec.push_back(ship->ID());
                 dropped_ships_fleets.insert(ship->FleetID());
             }
@@ -1800,6 +1845,7 @@ class FleetsListBox : public CUIListBox {
                     // TODO: moderator action to transfer ships / remove empty fleets
             }
         }
+        DebugLogger() << "FleetsListBox::AcceptDrops finished";
     }
 
     virtual void    DragDropEnter(const GG::Pt& pt, const std::map<Wnd*, GG::Pt>& drag_drop_wnds, GG::Flags<GG::ModKey> mod_keys)