I replaced some 3D models and the game stopped working.

Hello! I hope to explain it well: I am creating a truck with its respective trailer, everything is fine until I changed the 3D models of the wheels (the first ones I used had too many polygons), then this started to generate a problem, Unity does not indicate any error but the Truck can't go forward, only if I unplug the trailer, the truck can go normally. I never thought that something like that would cause a conflict with operation because the wheels don't even have a collider, they're just for viewing. I wish someone could help me. Thank you.