Mantis #7858: DeleteSceneObject done slightly differently. ProcessEntities now checks whether the objects have been deleted and, if so, sends an extra kill object packet, in order to compensate for potential race conditions encountered by the first one.

Note: I still cannot reproduce this problem, but I was able to emulate it by adding an artificial delay on ProcessEntities, which did, indeed, result in objects not being deleted. This fix fixed my emulated scenario.

OpenSim/Region/Framework/Scenes/SceneObjectGroup.cs

@@ -1987,6 +1987,7 @@ namespace OpenSim.Region.Framework.Scenes
         {
             // We need to keep track of this state in case this group is still queued for backup.
             IsDeleted = true;
+            HasGroupChanged = true;
 
             DetachFromBackup();
 
@@ -2010,7 +2011,13 @@ namespace OpenSim.Region.Framework.Scenes
                                 if (!IsAttachment
                                     || AttachedAvatar == avatar.ControllingClient.AgentId
                                     || !HasPrivateAttachmentPoint)
+                                {
+                                    // Send a kill object immediately
                                     avatar.ControllingClient.SendKillObject(new List<uint> { part.LocalId });
+                                    // Also, send a terse update; in case race conditions make the object pop again in the client,
+                                    // this update will send another kill object
+                                    m_rootPart.SendTerseUpdateToClient(avatar.ControllingClient);
+                                }
                             }
                         }
                     });