With the Main breaker on the distribution panel off the GFI outlet feeding the motor home trips. If I disconnect leads at breaker GFI trips. Disconnect leads feeding panel at transfer switch GFI does not trip. Disconnected leads between transfer switch and distribution panel and ran a temporary feed from the transfer switch to Panel main breaker (open), GFI trips. Disconnect temperary leads from main breaker, GFI trips. output Jumpers to generator contractor left connected throughout this process. Can there be anything causing a ground by tightening the leads at the contactor?