Trailer Chaining - hoses not connecting

[daemotron]

When attaching a trailer to a trailer (e.g. Brandtner Z18051), attaching the second trailer to the first works, but it's not possible to connect the hoses. Connecting the hoses to the vehicle works, so I suppose the trailer sockets are not recognized. When attaching in the vanilla game (without the mod), the trailer to trailer connection gets established.