To the OP ...
If you're still inclined to discount the argument that source power errors are much more common that many would think and that investing in a full featured EMS is an unnecessary expense you might want to take a look at pics of my own Progressive Industries EMS-HW30C. A series of 10 pics
start here, including 2 pics which clearly show an open ground event and another showing a low voltage event. Pundits can deny all they want, reality is I see numerous errors throughout each season, both while camping and while the trailer is parked here at home and plugged in 24/7. An EMS, while not perfect, is IMO an absolute essential for any RV owner that ever intends to plug into shore power. Invest in an EMS and the first time it saves your bacon you too will agree. ;)