1. The dimensions are standard for a RV small Microwave cabinet. You should be able to find 3 or 4 brands that will fit.
2. High Pointe---We replace about 2 a month at out dealership under warranty. They have a high failure rate. But, almost ALL the small RV built in Microwaves are cheaply made.
3. I would use the cabinet for something else or just go to Walmart and buy a countertop small microwave and it may fit in the cabinet without a mounting ring. You remove for travel and lay on the floor.
4. From what I have experienced as a RV tech, I would NOT buy another RV designed M/W. I would do item number 3 above.
5. They probably fail because they cannot handle the 120 voltage ups and downs that is prevalent in RV parks and the fact that some have Generators that have fluctuating voltage. Especially the Portable kind of Gensets. Doug