So I have just purchased a 2 new ram cards for my pc to complete the maximum 32GB ram capacity, and noticed that whenever I insert a ram card to slot no.3 the pc keeps restarting in repeat.
I had the same problem with my brothers pc, when after updating his BIOS, the ram slot worked properly.
I currently have the last BIOS update (moded to support my PCI NVMe card), and do not know what to do.
How can I debug this?
I tried reseting CMOS by removing the battery for a few minutes and inserting it back - still get the same result. 
and this is my RAM update (ram not in slot3): 
Ull have to troubleshoot all modules in single and dual channel first by brand and slots.
If the 2 Kingston modules alone, works OK in all slots as Single and as Dual channel and the existing Crucial modules were/are OK as always were…we can say that they dont like each other.
U got the issue with the already Crucial modules on it and added the Kingston later, if u do the opposite u should have the same problem.
Sometimes a bios update by the manufacturer works because something was corrected do to compatibility reports
But i think that ur issue is with the RANKS modules, the Crucial is single and the kingston is dual.
Due to the age of this mboard (B75…low chipset) model i doubt it that the manufacturer will provide u any solution…but u can try and report it.
Not pointing NVMe mod as an issue here or the 1866Mhz of the Kingston modules, STILL they are different modules…u should always get a PAIR of matched modules.
Kingston ValueRAM 8GB KVR16N11H/8 DS ELPIDA → 99U5403-159.A01LF and the other its a HyperX.
Hi @Meatw
and thanks for your reply.
After being on it for almost the whole day yesterday, I think i have found the problem (see attached image).
one of the ram pins looks burnt (?) and it’s top pin is missing.
and regarding to the RAMs - 2 where bought last year and 2 a month ago - both with the same specs. All four are HyperX
Glad u found the problem and sorry for a lost bank slot.
By the way…regarding specs, one thing is to see 4 modules in a shiny blue heat sink but wot matters is whats inside.
Merry Christmas, good luck.