Artifacts only in BIOS and during Windows boot, most likely caused by monitor

[Hpst]

I've noticed that about a week ago weird artifacts started appearing on screen during windows boot and in BIOS. They only occur when the PC was turned off for at least a couple of minutes and appear also on monitors OSD settings. They always disappear before windows boots to the login screen. I think I've already tried everything, plugging different HDMI/DP cables to differnet ports (both on GPU and MOBO), I reset the monitor, BIOS, cleared CMOS, enabled CSM and disabled full HD display in BIOS settings, flashed new BIOS. My monitor is AOC24G2SPAE/BK.
That's how it looks like

https://imgur.com/a/MMX5mYQ

View: https://imgur.com/a/MMX5mYQ

 

[Colif]

Have you tried the monitor on another PC?
does windows have drivers installed for the monitor?
That would be only reason I see why they disappear in windows. Seems windows fixes it... which is different. No guarantees it will keep fixing it though.
if it shows on two PC, its likely the screen is on its way out. Going bad.

most people seem to get horizontal lines, not vertical ones. I assume glitch is the green lines above the QR codes, or is it also the colours in the scroll bar?