Photoshop Marching Ants... 1 pixel off?

This is beyond me. I've tried scouring the internet, I've tried asking ChatGPT..
The only thing I haven't asked is Reddit (which is probably the first thing I should have done).

My CPU died so I had to fix my PC. After getting a new CPU installed, my photoshop started displaying problems specifically related to the marching ants shown when making selections.

It will display as if it's 1 pixel below and to the right of the edge I'm trying to select.
I say it's 1 pixel, because it's exactly 1 up arrow press, and 1 left arrow press to fix it visually.

If I try to move the selection so it properly covers the edge of something and mask/fill/delete -- it'll show as if I moved the selection. So beyond it being visually annoying, it's actually selecting correctly.

No -- it's not feathering
No -- it's not some ghost edge
Yes -- I've already tried all the performance settings
Yes -- I've already tried the view settings
Yes -- my monitor has been set to 100% zoom
Yes -- I've tested this on other monitors (I have 3)

I created a 100 x 100px canvas to show you what I mean.
The selection is made with Select All
If I create a new layer with 50% opacity, it will fill the whole canvas without any problems.
If I try to move the selection over to cover the small gap, it'll end up looking like the second image with an actual offset.

Any help would be appreciated.
Thank you in advance!

Marching ants selection with Select All

Result if Marching ants selection is \"fixed\" after selection