I think you have a mod conflict because myself and other people tested this tractor a fair amount, and there were never reports of LUA errors. Specifically with the cultivator means it's related to the cultivator or a mod conflict.
Yeah, you may be right, though I cant imagine what it could be. This happened both with a mod mulch/tiller and the basegame 3-point winch.
Cant be bothered checking though... as the mod is great and there are no lag or anything ;)