You know, it sounds so far from normal that I would wonder if someone who didn't know what they were doing attempted a repair, and got the door switches wiring miswired. Hopefully you don't hear the magnetron loud hum when this happens.
The way my Sharp microwave works, light on and plate spinning means that microwaving is in process, and if that happens with the RF shielded door open, you become human popcorn.
An appliance repair or microwave repair shop might have wiring diagrams and parts sources. Sometimes some of these lesser known brands like High Pointe could be relabeled models of other brands. A lot of the microwave parts are now generic. A professional in repairing this stuff would know the answers. But with the high cost of repair labor, so many technical things like microwaves are pretty much disposable.