Random crashes ITX setup

[Master_X]

Hey guys, I been troubleshooting a build for quite some time now. I have no clue anymore.

PSU is a Coolermaster V750 SFX GOLD. PC takes 400W max from the wall. This should be fine?

CPU is a 12600k and GC is a Gigabyte 3070 Ti.

The case is a Silverstone RVZ03.

RAM is Kingston 5600 but should not matter, defenetely working fine

 

The crashing is defenetely caused by something GC or PCIe related thing. Crashing is always different. Sometimes the whole screen flickers, sometimes artifacting, sometimes colors go weird.

That happened to me only if the build is finished. The case features a PCIe 3.0 riser/90° angle PCB. I got a 30cm riser cable laying around I used for testing. GC was not mounted and only laying on top of the case. Also bought a shorter one which fits the case. No problem at all if the GC is not mounted into the case. But maybe I just have been lucky because I cannot reproduce the crashes for sure. It's only in some games sometimes.

 

Anyone sees a problem with this build or has any hint? I also have some expirience with PC stuff but as I said I am out of ideas and tested so much.