X2
Open ground and 'you' are now the best ground it is finding!
Pick up one of these at the hardware store and plug it into an outlet you'll know in an instant what the problem is.
It's been my experience that open grounds usually start at the shore station outlet from overuse and the ground wire is pulled loose or off.
Plug the tester into the shore station first and if there is an open ground light tell the CG owner.
When parked at a CG I leave this plugged into an outlet inside my MH at all times. Let's me know at a glance if anything is wrong.