Then it would be best to check the version of your distro and session, then go to their github issue list and search for it, if there isn’t one provide a issue for them to look at. I also recommend verifying if it’s not a hardware issue or cable fault.

3 monitors here and working fine on Elementary OS, Super+P works as well. Are you on Wayland or X11?

Odd, at standard speeds right? 2133MT/s or 2400MT/s?

Did you test using memtest86+? The RAM stress test while running an OS is more guided for OC rather than memory errors. And no test can guarantee problem-free RAM, only that it does have problems.