TL;DR : when engine is shutdown metallic rope become collidable and prevent crane "buddy loading".
I was playing a 2 players hardcore multiplayer game with a friend.
I didn't have crane on my truck but my friend had one.
So the plan was that : he spawn a medium log, load it to my truck and transfer property to me.
It worked until a shutdown my engine.
I forgot the name of the truck, sorry, but i had 1 medium log cart + it's trailer. (i think the name are correct).
This setup have metallic rope above the logs to maintain them when fully loaded.
He loaded the 1st log just fine and transferred property to me easily with no collision problem with the rope.
However, when i decided to shutdown the engine, the rope became "collidable" again : when he dropped the 2nd medium log, the metallic rope prevented the log from getting in.
He took the log in its crane again, i started the engine and then he was able to drop the log correctly.
Probably an extremely minor bug that may not even need a fix but i report it anyway since it's a bug.
great game !
EDIT : We were both on PC.