First I am assuming you only get a shock while the trailer is plugged into a Shore Line as DC will not give a shock.
My first thought would be to check to make sure you have a ground in your AC supply from the house. Take a voltmeter and read voltage from the hot leg to ground. If you do not get a voltage there you have an open ground in your house circuit. If the ground is good inspect the Shore Line where it goes into and through the coach for ware in the cord to the hot leg of your AC power cord that could be shorting to the chassis. Do this visually all the way to the AC panel if possible or with an OHM meter, and all AC circuit breakers in the coach turned OFF, look for continuity from the hot leg of the AC line to the coach chassis. You should not see continuity from the hot leg to ground. Lets define the short and reduce the risk before we look for the reason the batteries went dead
WBCCI 12156 AIR 3144 WACHUNG TAC NJ6
2004 Excursion 4x4
1991 34 ft. Excella +220,000 miles, new laminated flooring, new upholstery, new 3200 lbs axles