Resume from standby - Power Good signal problem?

I have a Corsair HX520 PSU that I purchased for a new PC build approximately 6 years ago, from memory so could be slightly out but it is now out of warranty. I have built two systems using this PSU, the most recent just over a year ago.

None of the built systems has been 100% stable! The main problem has been returning from standby where it can be fine for many standby/resume cycles but once every week or two it fails to resume. I don't think this has anything to do with windows because brand new windows installs and old windows show the same problem. Disabling power saving does show some improvement, reducing the resume failures but not eliminating them entirely.

The voltages seem to be stable, the motherboard sensor readings and molex power plug readings via a multimeter.

I did read somewhere that some of these Corsair HX models did have a problem with the power good signal and I am wondering whether this could be causing the problems that I have experienced.

Does anyone know and can you shed any light on this?

I am thinking about replacing the PSU if it solves these problems but don't want to spend money if it does not help.

Resume from standby - Power Good signal problem?