Question re. tab arrows

[mantacid]

I had --somehow-- accidentally deleted my custom kvantum theme, but remade it from another one I had made. however, when I checked the preview, I discovered that the tab arrows looked like they do in the image. Why do they look like this, and how do I fix them.

[tsujan]

Tab-bar scroll buttons are painted as small tool-buttons with arrows but, for technical reasons, their background rectangle is filled with the window color. Depending on the theme, this filling may be more or less visible inside some widgets.