The radio on one of our tractors keeps shutting off, hit the power button and it usually comes back on same station, but sometimes will lose the station also but saves the presets. Figured it is a ground issue so took ground wire off and was going to clean paint of where it was grounded but with the ground wire loose the radio was still working. Guessing maybe the mounting screws are providing enough ground? Anyway wiggle all wires and everything seems fine as radio never cuts out when in shop. Put cover back on and when out in field same issue persists. Any advise on how to trouble shoot?