One of my pals at erm, not going to say where... was telling me that a knockoff VLVRs flooded the market to curb a shortage in Korean markets which resulted in more RMAs than usual for end users that noticed issues.
Semi-Layman terms. Theres a board part that regulates the 12v+ that has been off by more than the typical tolerance. It under-powers the devices attached to that rail. Some devices don't care, some devices are very sensitive to it.
Not saying that is what is up with your board and USBrx, but if you tried everything and are pulling your hair, then I figured I would pass this on. MSI, Asus, Tyan, Gigabyte, Foxxcon, and maybe more OEMs have had some of these [retroactively] bad bins work into production. Very small amount, they're all good at catching the errors for the most part. It happens often with so many damn components, but this one was enough for someone way nerdier than me to even bring it up.
Good luck though.
...and here is a trademark rant from me that pisses 90% of people off and displays my arrogance accurately (has nothing to do with you or anyone here).
These tech tidbits deep in the weeds don't ever make the news and 99.9999% of tech reviewers and vlogers don't know their asshole from a hole in the wall as far as actual electronics. They barely know how to repeat the specs written on boxes correctly. Thus why they stay in business, nobody sends real experts products to critique due to the risk they may actually know where to find real flaws and publish them. Either the news is flooded with product hype, or actual product info to help consumers. One is legal, the other is at risk of legal action. But they do matter. I know a lot of us have hardware out of warranty that we would like to repair, and if we could google the known problems, then weigh our skills versus potential outcomes, make better decisions, save on some e-waste, etc.