You model number should be on the frame of the microwave after you open the door.
Nat

My guess would be that the moisture/steam is getting into the control board causing it to shutdown. You might also want to check any bare wires inside the unit. Causing a short.
This brand is not one we are accustomed to working on as parts are not available from our normal suppliers. So these suggestions are just that, an semi-educated guess ;o)

Nat

Kinda sounds like the cavity thermal closed from to much heat which kicks on the blower motor to cool it down. The thermal should be restable probably by freezing it. The thermals are usually located in the control panel area. or on top of the unit behind the grill. sometimes there are two of them One is normally closed and one is normally open until to much heat gets in that area then it closes and puts power to the fan motor. Sometimes they are resetable sometimes they need replaced depending on the thermal You can tell if its restable because it will have two temp ratings on the thermal one temp when it closes and one temp when it's open. Thats my guess

What if this same unit runs, then stops while the timer keeps going? I open the door, let it sit for 10 seconds then it starts again. Sometimes it will just restart on it's own. Is this a contact issue as well?