50 ~ volts in door/doorframe, intermittently

I'm currently plugged in to my home using a 15/30 amp Hockey puck style adapter. However, the same thing happened at a campground while plugged directly into a 30 amp plug. So the adapter isn't suspect because it's happened both with it, and without it, and it's happened at 3 separate locations regarding power connections (my home, a campground, and someone else's home). All 3 locations, at some point, the voltage appeared to run through the doorframe, intermittently.

I was just out testing, I'm getting ~ 2v between ground and neutral in my GFI receptacle. Is that a problem?