Use Allocator.Persistent as sending data can take more than 4 frames.

Assets/Scenes/ARCollaborationData/TCPConnection.cs

             if (collaborationData.valid)
             {
                 using (collaborationData)
-                using (var bytes = collaborationData.ToNativeArray(Allocator.TempJob))
+                using (var bytes = collaborationData.ToNativeArray(Allocator.Persistent))
+                    // We use Allocator.Persistent above because sending data
+                    // can take several frames, so TempJob cannot be used.
                     SendData(stream, bytes);
                 }
             }