maybe the tim between the die and the IHS is only making contact where the 5 cores are but not the first core, but i don't think it would make that much diffrence in temperatures
other things i can think of is bugged bios and ad temp sensor
I updated OCCT to the latest build that came out and it seems to have bypassed rather than fix it. Had a successful hr pass at 4100mhz and core 0 went from 62 for the first few minutes and then it went to zero lol for the rest of the pass. I'll try some other programs out and see if it's the sensor for certain.
occt can sometimes be a bit stupid with temp monitoring. so i set up aida 64 to monitor temps and tell occt to read the data from aida 64.
with my old q6600 i used to do the same thing but use everest instead of aida.
sometimes occt would jump one of my cores up to 85c at idle and prevent me running any tests (and at the same time rendering any tests i did run a bit pointless as i needed to see the temps)
by using everest as my monitoring program for occt i didnt have that issue any more.