Newest twist.... DC-DC PSU decided to take extended lunch.

Yep, I chased the diode and both anodes connect directly to the transformer. I believe also those traces work back over to an opto, which makes sense.

Quick, OT question as this sort of helps me on an audio amp in which the front end seems to have a hard short and I could never figure it out. I have heard that when the driver IC or components within that fail to "oscillate", this can make the mosfet drive at full bore thus blowing the mosfet/fuses/etc? I suspect now this is why folks here recommended to run the amp at test with a light bulb or way to limit the current while determining if the mosfet is oscillating? I would figure if the oscillator IC did not work, the mosfet just would not turn on but......? Or is the failure mode shorted?

Just about anything is possible, depending on the exact drive connections and oscillator setup.
It could be permanently on, permanently off, or alternate between trying to start and shutting down.

A fault could also cause a dead short on the transistor.

Thanks for the help and education. I got the drive reinstalled and it has been running perfectly! I still don't exactly know what I did and if the replacement of those two caps did anything at all but it works. I cold started it about a dozen times now... No issues yet.