Question Memtest86+ errors

[O1111]

I've been getting stability issues lately (i.e. compilation of huge projects fails with random errors). Memtest86+ showed a few errors for memory slot B2 (I've tried both sticks from the kit and also a separate 8 GiB stick I bought just to test this), about 64 of them or so (8 here, but will be more if left for a bit longer):

In addition, I bought a new motherboard to test whether it is the problem and now I'm getting thousands of these errors each second in either slot:

Original configuration:
Motherboard: MSI X670E Carbon Wi-Fi
CPU: 7950X
Cooler: Artic Liquid Freezer II 420
RAM: 64GB DDR5 (Kingston Fury KF560C36BBEK2-64)
SSD: Samsung 990 Pro 2TB, 970 Evo Plus 1TB
PSU: DeepCool PX1000G
New motherboard (cheapest I could find with 2 M.2 slots): ASRock B650M-H/M.2+
CPU is the only thing (well, also the cooler) which was the same in all tests. Is this a dead CPU or still could be something else?
I'm quite sure I mounted it correctly as this is not the first time I'm installing a CPU into LGA socket, but 8700k worked without any issues previously.

 

[helpstar]

try latest memtest version 7.20
update the bios of your motherboard
clean the landing pads if the cpu with contact spray or isopropyl alcohol
be sure not to fasten the screws of the cooler too much, losen these a little and check memtest again
try the motherboard outside the case

 

[geofelt]

Even one error in memtest is cause for a rma.
Call Kingston customer support for a RMA; your ram should have a lifetime warranty.
Verify that your motherboard bios is current.
Many updates fix ram compatibility issues.