We just loaded it up on a server and had no issue getting into the truck and using it. Traded positions from driver and passenger and no issue. I'd say both download a fresh copy and try again.
Not sure what to tell you. Did a fresh install of the mod, and it's the same thing. My guest player in my game gets into the semi. Moves on my game, doesn't on theirs. They can't get out of it, and have to leave game.
