I project I inherited had a welded pedestal, one of the few parts that never gave much trouble - until we started to make them at a South African subsidiary - suddenly the circuit breakers there wouldn't fit into the pedestal - everything was checked and was clearly 'to the drawing', but investigations revealed that the actual original pedestals had a bend of 30 degrees, where the drawing showed one of 60 degrees.
I went to see the chap who made them in our factory and asked him why he made them like he did - "I knew it was wrong, but nobody would listen, so I just gave up and made them right. Inspection never noticed, anyway."