Terrible performance degradation after rendering for no reason?

Question

Intel

In general, such a thing.
There is a wonderful station from:
Motherboard
Processor Xeon X5460 (stock - 3.16 --- overclocked to 4)
Operational Corsair Vengeance 2x4Gb (1600) Voltage
per percent - 1.4, for operational 1.6
with such overclocking, I think it’s quite adequate)
Suddenly everything started to shamelessly lag (even after resetting to stock voltages and frequencies)
It’s definitely not in Windows - everything is checked rechecked
A couple of days before the start of the lags, I rendered a video (about 11 hours) - which was successfully rendered .
I controlled the temperatures - I repeat
. What could be the reason? (no overheating, system is clean, tests pass)
And you can without - "throw out buy newer!"
Thanks

Answer 1

Maybe something with the disks?

Answer 2

and you do not mind that the maximum temperature for this processor is TCASE 63°C ark.intel.com/ru/products/33087/Intel-Xeon-Process...