I measured 320W stock.
Also CX500 has only 34A on the 12V line, so might not be enough for overclock.
I have 3 cx500 and all 3 miners are overclocked and working just fine without problem.
I am not surprised, but you are reaching the limit of the PSU, so it might die sooner than later

Cx500 max 36A 456W. My ant too works perfect for 2 months now on cx500. Ihave 220v ac power if that matters.