Strange white lines that only show up in videos

[My PC Parts](https://pcpartpicker.com/b/Dd3tt6) On Windows 10.

Oddly, [these lines can be screenshotted](https://imgur.com/a/vnw9EYr). So they're obviously not dead pixels. The nature of them is a small white vertical strip shows in the lower left of _YouTube videos_, but upper left of _Amazon Prime videos_. Once I go fullscreen the line appears, and usually blinks for a few seconds then goes solid. They're never present during normal use, not present in VLC fullscreen videos, not present in fullscreen photos or games. Seemingly just YT & Prime.

This started happening recently, about a week ago. I've never seen anything like it and can't think of what the issue could be. Help would be appreciated.