I am having a similar issue, only with my a/c and microwave. Generator works until I put a significant load on it, then quits generating, but still runs. I suspect bad brushes or corroded slip rings in the generator. No circuit breakers are tripped, not even the one in the generator. I am taking it in this weekend to be checked out.
A/C is new and works fine on SP.
Burns & Diane
2005 Winnebago Aspect 26A/2012 Subaru Impreza toad
Illinois! - Where the politicians make the license plates......