Yep, the hinged lorry in the game files. Some of the Russian modders over at playground.ru have tried to mod it back in but had the same problems you ran into. I’m guessing the reason the trailer stops when you get closer is because the multi-staged physics system only loads the vehicle’s handling parameters when you get close enough to physically interact with it. As for modding it back in with Lua, I seriously doubt it’s possible without reverse-engineering or stumbling on the correct string as it’s a completely unique vehicle attribute.