Exercise genny while on shore power?

Bobbo wrote:

I'm glad you said "very little possibility for it to connect to both at the same time." That is tacit admission that it is possible and could happen. That is the perfect rationale for unplugging first. Small risk but large consequences, with piddly (a technical term) effort required to absolutely prevent.

Yes, I admit that it is possible. Lots of things are "possible". But understanding how an ATS works tells me that it is highly, highly improbable for the ATS to connect to both shore and generator at the same time. Switching with heavy loads can cause arcing and damage the contacts, possible making them stick, but they can still only make contact with one side or the other, not both. An ATS is just a large relay.

Yes, we hear of the occasional claim of it happening, but very seldom (among 100s of 1000s of RVs in use), and never have I been convinced that what the poster "thinks" happened actually did.