I wanted to update you that I received your unit and after testing, I have found nothing wrong with the unit.
When I recieved your unit was in 480p resolution, which indicates that your Forced Reset of the [Output Video Resolution] was successful. I've switched back to 4K output with no issues. The firmware was M36.R.173, I was able to update the unit to the M36.R.0175 firmware. Both before and after the update, the unit has been outputing correctly. I'll do some long term testing but at this point the problem that you were experiencing does not appear to be an issue with the Bluray Player.
I've received the new unit, and have been using it with the same connections and everything has been working flawlessly so far. The only difference in setup with the new one and old one was, I set Quick Start to 'off'.
What do you think went wrong with the old unit? Could you keep me updated if something changes?