G3RDAS
If I got your issue right, all hardware ( monitor, cables ) is same ?
Try to reinstall windows to win10 1809 build 17763.1098 ( it works for me good: you cannot find exact this build, but you can find a bit older build 17763.XXX and install updates upto 1098 ), then block win updates
Then, try to setup Intel grapfic panel + drivers of ~2018 year. Someone here wrote he installed 2016 year drivers to solve issues, set full range in grapfics, 8 bit mode, turn off all display energy-savers, check in Ditherig no dithering enable