Red light on motherboard

[I kill Bunnies]

I have a Z490 motherboard with 10700k and Noctua NH U12a fan. Recently my PC was crashing due to overheating so I re-applied thermal paste.

This seems to have stopped the overheating, but I still have a red CPU QED on the motherboard. Should I be worried about this? The CPU fans are all connected, the CPU itself seems well positioned and I have applied new thermal paste.

The motherboard manual unfortunately just states I should investigate if this light comes on.

 

[I kill Bunnies]

It's an

ASUS ROG STRIX Z490-F​

 

[I kill Bunnies]

It's booting fine, I played a couple of games of PUBG. All fine.

It's a Noctua NH U12a fan. This fastens to the back plate with two screws and first one is part screwed, then the other fully and the first is finished. I don't think I could do it any better if I had to re-do.

 

[I kill Bunnies]

OK I followed the video and it seems to have worked, although every now and then the red light comes on briefly.