Some elements are not visible on some pages

[wehkah]

On some pages some elements are not visible, for example the YT home button and the button for subscripted channels at top left position on YT. The buttons are there, if you hover the mouse over it, you can use them.

These and other elements are invisible regardless to which mode I set the addon to.

I am using FF in KDE-Neon, my desktop is set to use "Breeze-Noir-KDE" as theme, and I installed the GTK version of that theme for FF as well.