Could you send me the save file? I can't reproduce this issue with the minimal set of mods, so something else is at play.
I don't know what you mean by saving files.
To reproduce this problem is very simple, map editor - create a new scene - start the game - put a car on the ground, and then put a loader, which will report an error.
If I close all other modules and only open this module, an error will be reported.
My English is not very good. It's translated by computer. I wonder if you can understand it