Help stabilize 9900KS overclock - water cooled!

[Alexauwa]

Hey guys,

I finalized my first custom water cooled pc and are very happy with my results. Still, I have some questions in terms of dialing in the right bios settings.

I run the following setup:

// PC
i9 9900KS @5.2 GHz
Gigabyte Z390 Aorus Master
64 RAM 3200 CL14
GTX 1080
1000 Watt PSU

// COOLING
2 x 360 radiator
EK Pump
EK CPU cooler
Heatkiller GPU cooler

I run the current bios settings:
CPU clock = 5.2 Ghz
Memory set to XMP
Loadline calibration = turbo (level 6)
Enhanced multi core performance = disabled
Uncore ratio = 47
C states = all disabled
CPU vcore current protection = extreme
Pmw phase control = extrem perf
Power limits are not limited
Rest voltages are set to auto

In terms of vcore and maybe related settings I have questions. I started off with a vcore of 1.290. I played around 1.290 and 1.310.
I tried Cinebench R20 and R15 a couple of runs. AIDA 64 as well and Prime95. All seem to work even with 1.290 vcore at the beginning. The longer the pc was running the more I run into crashes. My temps are absolutely fine. In between 80-85 on prime95.

So my question: is it normal that the vcore of 1.290 is not enough over time? Does it need a higher vcore over time? Do I have to keep raising the vcore? What additional bios setting would help stabilize the overclock apart from the vcore?

Memory is not overclocked and GPU got 200 MHz and 100 clock overclock though.

Thanks a lot for your help,
Alex