Corsair AX860 - Potential fault?

Hi all,

Long time lurker first time thread starter.

I've got an original Corsair AX860 (not the i) which has been serving me well for the past 7, nearly 8 years.
It's been the only thing I haven't changed in my PC as I'm a tight ass and don't want to buy a new one and new sleeved cables...

A couple of weeks ago I was playing a game (Satisfactory) when my entire PC shut down (almost as if it hit OCP or something) and my GPU fans hit 100% and sat there, I sat there with my heart in my throat contemplating my existence.
There was an electrical burning smell emanating from my case however as it was fully enclosed, I couldn't pinpoint the source of the smell.

I switched my PC off by the PSU switch and left it a minute to allow power to drain from the caps etc.
Then, with very clenched buttox, I flicked it back on and powered up expecting all 2 grand's worth of PC to be dead jim... and it powered up absolutely fine...???

*touch wood* - It's been 3 weeks now and I've had no other problems??

Any ideas what may have caused that bizarre shutdown and smell, especially as it worked fine immediately after?

I'm looking into a new PSU at the moment out of necessity (New Corsair AX850) however am curious as to what had a hiccup?

Thanks :)