Hm that's still quite low honestly as intel sets a max of 1.52 i believe while people accept 1.45 as the absolute maximum for air & watercooling if you are pushing the chip too its limits. (Some people push 1.4v on proper watercooling systems closer too 4.8 - 5 ghz) Sure it didn't burn the memory controller on one of the channels there on the motherboard rather then a cpu core ? seems to be more common to do then cpu cores. Id give it a go increasing memory voltage slightly as well while the rest stays at its standard settings in the bios including ram speeds too the standard specs of ddr3 or ddr4. (Bit above whats specified on the memory sticks is worth trying as well, like me running my ram at 1.56v instead of 1.5v for stability. (Got ddr3 here though so will be lower on ddr4.) 1.35 i believe ddr4 is at right ? So 1.38v running at the standard 2133 mhz should work for testing if you do have 1.35v ram. & checking if the 4th core is still stable if you undo any overclocking for now that you got with 3 cpu cores.