ALmost happened to me. Led me to a sort of a not joke.
Many RVers have a few screws loose.. WHEN those loose screws are the ones that attach the wires to the neutral bus on your power center... Well, you know what happens then, You saw the result with your own eyes.
Also check all the other wires (Do this while not plugged in or running generator).
Other places I have found loose screws includ the shore plug, shore cord outlet (if detachable) and RV inlet (if shore cord detachable)
I have not found loose wires in the auto transfer switch but then I've only worked on one and that was a warranty replacement by a competent dealer tech so I'd guess he re-tightened (Well for a fact I know he did) when he replaced the original. Do not know if the original was properly tightened or not.