White line across bottom of screen

[Janik]

Using Cinnamon 4.6.7 on Linux Mint 20, there is a white line across the bottom of the screen. It is just a few pixels high but distracting nonetheless. The issue seems to be caused by the Window-Border, since it disappears when changing the style of the Window borders to another theme in the Themes UI. The line only appears when there's a fullscreen window present on the screen, regardless of whether that window is focussed or not. It is not visible on screenshots.