Just a thought but did you have the exhaust fan running when you were operating the microwave?
The microwave MAY have a over-temperature protection feature that shuts the microwave down if it over-temps. If properly vented, it should either vent outside through the same vent used by the exhaust fan from the cooktop or it may vent upward over the top of your microwave into your RV's kitchen.
Check both of these outlets to ensure that the heat from your microwave is venting somewhere. It not, you may have to remove your microwave and check for an obstruction.
Jeff & Laurie -- Full timing in Rockport, Texas
Auggie (our beer-loving English Cocker Spaniel)
Angus (55 pounds of attitude in a 5 pound chihuahua body)
Our home base -- 2018 Grand Design Solitude 375RES -- The "Uno Mas!"
The mobile office -- 2016 Crossroads Hill Country HCT26RB -- The "Poquito Mas!"
Gone but not forgotten: 2015 Heartland Landmark 365 Key West (lost to Hurricane Harvey)