Every RV owner should buy a non-contact voltage tester and outlet tester. Together they cost about $30 and can literally save your life
. Before I started doing this, one day my kids washed our camper in their bathing suits and later I went out to the camper to get something and got zapped when I grabbed the door handle. The kids could have been killed. It turned out to be a bent ground pin on the 30 amp extension cord I was using, which I usually didn't use at home.
Test every single time you plug the camper into an outlet!
Both tests take less than a minute, total. Mike Sokol has an excellent safety series about RV electrical safety, a few of the important points are at the links below.
Doing these tests would catch problems like the ones mentioned above.