once should be all it takes,I remember 1 time getting a charge back for a service call on one of my jobs when the problem was the wife of the customer decided to remove the equipment that I installed so she could dust and hook the cables up in reverse,thats when I started to take photos of my work ,just to back it up for the record
This is CABL.com posting #158516. Tiny Link: cabl.co/mPoS