Focused window bleed onto second monitor

Amazingly it seems to be fixed in windows 11 insider preview for me :) - That was one of the first things I tested and all windows on all screens are staying on their own screen..

Update: This persists into the Windows 11 Insider Preview I just received. The above fix also doesn't work because you can't relocate the taskbar for some reason.

I just noticed this problem today. Been working fine for a few years, but after windows decided (without my permission) to update to 21H1 this started. I did a regedit to stop the updates. But I read that it doesn't work now days.. And this seems to have been an issue for over a year, and still not fixed with "new and improved windows 10".

OT: I'm using the machine as a media server for the family and would like to keep it online 24/7, but now after the first update got through it decides to update almost every night. Which mess up some stuff that I need to manually fix every restart.

This is the reason I'm thinking of going back to Linux. Only problem is some applications don't work as good as it does on windows. Which is a shame.

Note: I haven't enabled updating just for this reason. Something always stop working or adding to the list of defective stuff.

Edit: A weird fix is setting the taskbar on top. If you're using 3x1

This issue is still present as of Insider Build 21390.co_release.210521-1658
I've been dealing with my lower monitor having title bar bleed to the top monitor on maximized programs for ages, to the point that I moved the taskbar to the top of the upper monitor to stop having to deal with taskbar icons being obfuscated. The following screenshot will illustrate how window title bars from the lower (1920x1080) monitor bleed onto the bottom of monitor 2 (2560x1080). Windows notifications also pop up on the lower monitor's upper-right side, then animate up to the upper monitor. Edit to add: This only impacts maximized windows. Windows in fullscreen (games, videos, etc) do not bleed over for me.

Lending support to the idea that this is a bug with Windows.

Here's my setup:

The bleeding happens from the top of monitor 2 onto monitor 3, but not in the way I think any one of us would expect.

All monitors are running their respective recommended resolutions, with no scaling applied anywhere. All three monitors are running off the same GPU.

This is maximizing a window on monitor 2 and having artifacts of it bleeding on to the bottom of monitor 3.

Firstly, it is not just the top-most pixels bleeding over to the other monitor:

Here, you can see that it's the LOWER part of the tab in Firefox that bleeds over by looking at the Blue and Yellow colors of the squares, or the bottom of the Google or Firefox logos. This would seem to indicate that this is not an over-scan issue, or other display-related issue, because a select strip, partially down the screen on the 2nd monitor is duplicated up to the 3rd monitor.

Secondly, it depends on HOW the window was maximized.

This is the result of "bumping" the border between the monitors at roughly the center of the lower monitor:

This is the result of "bumping" the border between the monitors, on the left 25% mark:

You can see how the artifact that's generated along the bottom of the 3rd monitor can be controlled based on where I drag the window from (vertically) and where I bump it on the screen horizontally. Note the subtle differences between the height of the blue and yellow squares and how much text you can start to see in the three examples above. Note the difference in horizontal position of the highlighted browser tab in the lower two examples.

What seems to be happening is that, after "bumping" the top of the screen, it generates an artifact related to what was on the 3rd monitor when the maximize happened.

Finally,

If I hit "Maximize" on the window instead of using the "bump" gesture, I get a white line across the bottom of the 3rd monitor. Which seems to be the same kind of white bar that the OP shows along the vertical border between their monitors.

This seems to indicate that, during the maximization process, the code that handles the maximization of the window neglects to properly clean up portions of the window that were off-screen during the maximization process, for whichever screen a window is being maximized on.

Since I can control what the bleeding looks like, I do not believe this is in any way related to an issue with the displays themselves.