the instering issuse with vending machine i did see alot of older unit and i am sure it will be getting pretty messy with new code required gfci on it and yes of course the commpressor do have some current leakage but there are few other source can have current leakage as well.
i know one vending machine did have heat tape inside the soda vending machine and the tape was rotten for some reason and show up with current leakage and replace it.
Merci, Marc