Weird display glitching - what's at fault: display or cable?

I tried searching for months if something like this happened before, but I can’t find it.

The laptop is pre-owned, under my watch, I haven’t dropped it or did anything that would inflict damage, it came with this scuff:

At first, it functioned normally, but a month after I went to get a glass of water, to come back a minute later to it doing this.

There’s a line at the top of the display, things at the top of it aren’t glitched and look fine, everything below it has a sort of ghost of the entire display.

This is the line in comparison to the scuff mark.

The whole display. You can kind of see the duplicated menubar below that line.

Here’s the “ghosting” in more detail.

The display has weird glitching, it happens randomly now and then and lasts less than a second, like a flash. Here I caught it in a glitch:

And no, the window isn’t being moved, looks like it just made 3 duplicates. Also should note that this too, only happens below that weird line.

HDMI output works fine without any glitching, so I’m guessing that it’s not the graphics.

It also doesn’t seem to change the rate of glitching or how it glitches depending if I press on the display or mess with the orientation of the hinges.

Hope someone can help, thanks in advance!