Any explanation?

[InputLagger]

Guys, try to unplug your psu power cable and then press the power button of your pc for 20sec or so (to unload all residual current) then replug the power cable and start a game.

For me it works everytime, the first game after doing this feel smooth and everything register but it quickly deterior...

I've tested it and it probably works. Before the test, I got 92 kills on moving bots on Aim Botz map in two minutes and after the test, I got 108. Usually, I can't achieve more than 100 kills. Also, mouse movement has changed. It feels like the sensitivity got lower and the crosshair slightly lags before my hand movement but not in a bad way like when you have noticeable input lag. It almost feels like a negative acceleration. When the mouse behaves in such a way you can easily stop the crosshair right on the enemy's head. Usually, I can't. It's always a little bit further or a little bit behind the enemy, so I have to constantly micro-correct my aim. Crosshair is floating around the enemy's head and I have to struggle with it.
Also, sound quality somehow has improved. I wasn't expecting that at all and was really surprised when noticed it.

Try to electro isolate power supply from pc case