In this clip you can see that the Construction Rig Semi Trailer which the other player is pulling appears to have its legs extended as if it was parked. It's may not be visible in the clip but when he parked on the bridge, rear wheels of his truck were lifted off the ground due to extended trailer legs. Of course on his end everything looks normal and the trailer has its legs lifted.
Here not only legs are extended but the trailer appears to not be mounted to the saddle. It looks as if he was dragging the trailer on a winch. I tried changing traveling to a garage on a different map and then going back to my truck (sometimes that fixes synchronization issues), but it didn't help. Even after we both traveled trough the gateway to a different map the problem persisted.
In both cases I was the host of the coop session.