50 ~ volts in door/doorframe, intermittently

One common thing in all the discussions I have read about this thread would lead me in the direction of replacing the shore power cord its self. The reason I say this is it is a strain point at the connection to the shore power source and again at the M H entrance point. over time a ground wire may have broken on either end inside the cable/cord and left to open when the wind blows or some one walks on the floor and the home sways. This is a common problem in the industry i worked in. One way to trouble shoot it is to disconnect it from both ends and put a continuity meter on the ground lead and one of the power leads on one end and jumper the same two leads on the other end REMEMBER BOTH ENDS ARE DISCONNECTED.have one person watch the meter for deflection while another one starts at the other end flexing,bending and twisting the cable to produce the open if it exist in the cable.go slow about do a few feet of cable at a time.try not to move the meter end as this could cause a false deflection.I would also at this time be looking for pin holes and abraded areas on the cable/cord. A lot of times we look for a major problem when its the simple ones that bight us in the butt.