Question MSI x370 Gaming Pro no post with cpu error (working cpu)

Aug 8, 2019
I hope someone around here could help with this:

I have a..
Ryzen 7 1800x @3.85Ghz 1.35V
RAM : 4* Kingstone HyperX fury black 2133/14 (2 * Hynix C + 2 * Micron D) @2733/14/16/34 (1.36v; VPP - 2.51v; VREF - 0.68v)
MSI x370 Gaming Pro (7A33v4G BIOS)
MSI Gaming X GTX 1080 Ti
Windows 10 1903
Seasonic prime platinum 1200w
Noctua NH-D15 cooler
(all OC ran stable for at least 1/2 year now)
My problem is the following:

I wanted to adjust the RAM clock/ voltage due to the hot summer weather and when I saved the settings (2400 14/15/34; 1.33v; VPP - 2.51v; VREF - 0.68v) the system just wasn't booting at all. After I short the power switch pins, it immediately turns back a "CPU failure of failed to detect" code (CPU error LED around the 24pin connector).
I had a somewhat similar issue when I tried to mess with the ram timings, but it's a little bit different. Last time it was the same error, but the system wouldn't boot at all, it came back after I installed a DIFFERENT cpu into the board and even that took around 3-4 tries before it kicked in.

Now I just waited around 12 hours (with the PSU turned off) and the system just suddenly booted with a "unidentified error prevented the system from booting... (reset or load profile in short)".
I choose to load the previous stable OC settings, and it worked!.. for like 14 hours, when I got a crash report "Page Fault In Nonpaged Area".. I thought it wasn't a complete reset and it kept some wrong ram timings, but when the system restarted:
At first, it was a blank black screen (the display detected the PC because it turned on and displayed a blank black screen) and the board indicated a "VGA error/ not detected" error.
I used hard reset because nothing else worked and HERE WE GO AGAIN: CPU failure of failed to detect ....

Yes, I tried:
-bios reset (even with removing the battery)
-start without cpu/ram/vga (even only the board itself without anything attached)

I really hope someone smarter than me could help me out and thanks in advance!