Sharp Microwave Drawer always trips breaker

Sharp smd2470asy, built in 2017. Bought used from some Russians (I know...), but it was $300 instead of $1300. It worked when they demoed it, worked the first time I used it at home, then failed. Made a weird noise, weird smell, the microwave wouldn't heat after that so I took it back. They 'fixed' it, and it was working again for about a month. Now when I start it, it runs for 2 seconds and then trips the breaker, every time. I went the easy route and replaced the 3 door switches. It worked again for 2 days, now same thing.

I tested the high voltage capacitor and it seems fine. Thought maybe one of the switches I bought was bad, so I tested them. Independently, they work fine. But the one switch that's Normally Closed only works properly when the microwave wiring isn't hooked up to it. Basically, the switch works as normal as tested by a multimeter, but when I attach the red wire to the NC terminal, I get a beep, so I'm guessing the switch is fine, but there's a short elsewhere in the circuit? The red wire appears to run to a board in the back and is attached to a couple of power relays (DEC DU1PU 24VDC Power Relay 4Pin 16A 250VAC). These test fine as best as I can tell. However, they finally get routed to the Transformer (RTRN-B101MREO-DM). There's an orange wire going to one of the leads of the primary coil and when this is disconnected, the Normally Closed door switch operates properly. I have tested the Transformer coils and they read properly, but I'm guessing there could still be a short in it? Looking for some advice. Do I replace the transformer (kind of expensive) and hope that's the issue? Can I test it further? Or could it be the magnetron?