The transfer switch on the RV is there ONLY so you don't have to do the manual plug switch
It is not there to switch power sources under load..aka A/C is running
This causes arcing and pitting on the relay contacts
It's only a matter of time before it malfunctions because of this
Yes they are make before break
But most do not have mechanical interlock , and many 50 amp switch have two relays in the box, with out mechanical interlock if one set sticks, both can be connected
Do this with two power sources and you are going to blow up a generator
It has happen..It has been posted
They were non believers before it happen to them