Question about a coaxial cable electromagnetic field / possible interference with monitor / PC

[alindefaugh]

Keep us posted with how you get on.

Ugh I moved the entire setup to the adjacent wall. It's really terrible.Forget input lag, the monitor image is just bad in-game, can't even concentrate at all, I played couple unranked match and it's impossible to play like this I hate it

I'm kinda ashamed to say this only now , there are 6 cables running along this wall on the outside (I'm on the outside building corner ) 2 of which are thick. They are coming from a different appartments block in front of this one. I just forgot those existed. PC case and monitor are parallel with these cables within maybe 30-50 cm depending on how thick the wall is. Before both were perpendicular to the outside wall at about 1.5 m distance from it now they are parallel with it within cm

Speechless

 

[Newmarket]

You won't be able to make any useful measurements with a DMM or similar. You'd need 'rf' detector equipment / probes and in your environment it would likely be fruitless in any case.
The type of problems you are describing seem unlikely from a cable TV co-ax. If it were the cause then I'd expect greater problems such as becoming unusable and resetting. But never say never !
There's a possibility that the geometry of the coiled up surplus' cable could have caused the problem.
If it's still an issue you might want to try snap on cable ferrites on the coax where it enters the room.
Use one that is big enough for you to loop the cable through it once as this increases its effect.
Also where is the screen (ie outside of any coax connector) going ?
Is it showing continuity to a metal equipment chassis ? And , if so, is that chassis connected to 'Earth'.
Any connection scheme here may help / not help / make worse - since you don't really know the arrangements at the other end. But you can 'cut and try' to see what, if any difference, you find.