Computer Repair Job - Bedfordview, GP, 2008

I have a randomly freezing PC. I’ve tested the memory multiple times using memtest86+ with 100% success. I’ve disconnected all hard drives and peripherals and booted from a live USB - the freezing still happens. So it’s definitely a hardware problem. The freeze causes the screen visuals to become static and is only fixed by hard restarting the machine. I’ve tried an old GPU to no avail, experiencing the same symptoms. I have gotten an error recently upon boot complaining about a CPU system fatal error, something about MCE that I wasn’t able to catch. So I assume the CPU is faulty now. It’s been running for a couple of years just fine though. Although, in November last year I did change to cooler to an nzxt aio cooler. I need assistance in pinpointing the problem as it may be CPU, Motherboard or even power supply. Relevant specs are:
B550-E gaming motherboard
Ryzen 5950X CPU
AMD 7800 XT GPU.