If you get the shock when plugged into shore power, there is only one thing certain, that the frame of the RV is not grounded via the shore power cord. The problem could be that the outlet isn't properly grounded, or that the ground wire of the shore power cord isn't connected to the RV frame. Nothing else is indicated by this shock, as a correctly wired RV will give a mild shock if it's not grounded. There could be an additional wiring problem, but you have to get the ground fixed first. Best to not use the RV until the fix is made.