Well, get it fixed right, but know that the original Apollo "Halftime" Microwave Convection ovens used in Heartland RV's were originally designed for TABLETOP use, not for use in an enclosed cabinet. The vendor who sold those microwaves to Heartland modified them with a squirrel cage air blower mounted to the top back of the unit, and wired into the microwave's cooking circuit. This blew hot, humid air out of the microwave cabinet enclosure through the trim bezel vents into the RV interior. There was no external vent.
When I bought a replacement Sharp Microwave oven, I added a similar squirrel cage air blower to the microwave and wired it into the cooking power circuitry. I had to modify the plastic microwave foot mounts that screw to the bottom of the cabinet, and fabricated a metal tie down device from hardware angle brackets, screws and nuts. I kept the old plastic bezel, though I had to repair it with black epoxy.
The add-on blower blows a very strong current of air out of the microwave enclosure, and I assume that a very strong current of air is coming in the other vent slots in the bezel.