Two thigns I have had do that....
AN open ground will put the chassis and metal parts connected to it at 60 volts relative to either neutral (Which is bonded to ground elsewhere) or hot. (This is on a 30 amp RV. on a 50. it might be a different voltage or even zero, higher if plugged into 30)
This indicates an open ground. HOwever though you can measure 60 volts, or close to it, nearly no current flows.. The reasons are technical and Well. One of the many classes I took in college explained it rather well.
However another issue I've seen is a polarity reversal. For some reason it did NOT trip the breaker (I know the ground was good) but that dang trailer would knock me for a loop if I touched two metal parts INSIDE the trailer.
I finally figured out what the prior owner had done wrong and fixed it.. He was, like me, trained in electronics... But unlike me he was NOT cross trained in electrical. (Black means different things depending on which hat I'm wearing).