Typical of RV workmanship, all campers should come with a wiring diagram, any changes made due to optional equipment noted on the schematics.
You could buy a simple clamp on amp meter, they are very inexpensive, measure the DC current drawn by each jack motor and compare them, one bearing could be worse than others, or you could just take them apart and grease them all up.
These little meters are very good for checking the current drawn by your furnace, fridge etc., especially if you use solar.
Meter for troubleshooting camper electrical problems.