I did repaste originally when I had the issue, I have had it since I built the PC back in May, so I don't know about RMA. And HWinfo64 does appear to show them all at similar temps, so thank you @SpookyCitrus
I bought an i5 9600k back in May and have been living with a hot core ever since. I have no idea how to affect the hot core directly to disable it at this point. I have an ASRock Z390 Pro4 motherboard. The screenshot of Open Hardware Moniter is at idle a few minutes after reboot.