I decapitated the 9900k with EG starts delid tool on Amazon. Then used this plastic razor to cut through the "solder"
It went through the solder like butter without much risk to die. Solder was like a alumunium sheet
Then buffed the die with some polish on a rag no need to sand anything. I'm doing direct die watercooling. Also setting up my first custom loop but lacking 2x 90 degree fitting b4 I can fire the system up. Should be up and running tomorrow if I didn't wreck anything.
Having the chip at 5ghz I would say cracked die highly unlikely, seeing that difference amongst cores direct die makes me think bad thermistor. Once that diffusion barrier is broken I wouldn't think it last long with oxidation from the air.