Hi Finn, I am not sure. When exactly do you get this message? Is this related to creating new connection prefabs through General Settings? What is the setup of this particular connection prefab? Perhaps you can email it to me in a unity package? In general I would recommend to always use the latest version (please backup the project first, just in case ) which is 8.4. But nothing has changed for dynamic crossings lately so I am not sure if that will resolve the problem. Or is this related to custom connection prefabs? Thanks, Raoul [UPDATE] This seems related to custom connection prefabs. Could you check this on beta 8.4. and send me the source model if you still get the same warning?