Maintenance would be on the driver since it's his responsibility to shut down the truck. U-Joint failures happen (on the tractor), but should be inspected daily (finger quotes).
Doesn't matter though, cause he left his bed up. There's no driveshaft on the trailer. If there were, it would take forever to hook a trailer lol.
3 years helpdesk, just over 10 years now truck driving. Pairs well with selfhosted media at the house, but not working on other people's shit.