Cannot enter UEFI anymore, on two AM4 motherboards

Hello.
First problem arose on an x370 taichi motherboard. with ryzen 2700x.
At one point I noticed that I cannot go into the UEFI anymore, just a white charachter cursor appears, and then everything frozen. (cannot turn on/off num lock on keyboard). I associated this even with the changing of RAM modules, it was about at the same time. I trid reflshaing, downgrading,upgrading bios, resetting settings, many times, nothing worked.

Now, a year later, same cpu, same RAM modules. HyperX Predator 3000mhz HXC15PB3K2/16. But brand new Fatal1ty B450 Gaming-ITX/ac motherboard. I noticed that windows can only use 8 out of the 16gb installed (8.1GB Hardware reserved), and tried to debug this problem. At one point I did reset bios to defaults, saved, and rebooted. After that I could never enter UEFI again. I tried reflashing to the same version (3.70), resetting the settings with the jumper.. two times each, it didn't help. At least this motherboard is in warranty and i can send it back.

I identified I have faulty RAM module and put it aside, but even with good RAM, it does not want to enter UEFI anymore. I have a feeling there's some bug in the asrock AM4 bios code that the faulty ram triggered and maybe did some permanent damage ? I don't know what to think, this is too weird.

If you have any suggestions on how I can restore my UEFI access, please share. Yes, I did try the asrock restart to uefi utility, it just freezes like normal pressing of f2/delete (shows a white underscore charachter cursor in the upper left corner in the middle of the screen, and that's it.).

Dead forum ? :\