AC shuts off when on generator
What you are describing is the transfer switch trying to reengage (A thumping sound). Others on this forum are starting to post they are having the same issue. It seems to be pointing to the transfer switch "dropping out". Of course it will not re-engage until the AC's are turned off.
The reason the switch is cutting out is because of the heavy power draw from one of the AC's, though it should not cut out.
My first guess would be the transfer switch, after that the generator. In rare cases it could be the AC units compressor being bad.
It should still be under warranty so unfortunately I would insist on them fixing it.
By the way, you won't need to check to see if you are getting 110 volt because you will not have 110 volt since the switch is what sends powers those items.
The transfer switch is the device that "switches power" from the shore power cord or the generator to the coach.
Keep us posted when you get it fixed.
2013 Georgetown XL 378
2008 Honda CR-V