@leocg I have this same issue. Bascially, you hover over a tab and it highlights as expected. However when you ove the cursor the highlight is still there. It is supposed to disappear after you stop hovering but that doesn't happen for some reason. Of course, it doesn't hinder the overall functionality of the browser, however, it is visually annoying to look at and I prefer the look previously. Here is how mine looks like. Note: I am using the older UI, and I do not want to update to the new one.

My problem is very weird. I don't know why, but this problem started out of the blue, and before it wasn't like this. I would hover my cursor over a tab, and it would highlight, and when I took it off, it would stop. However now, it doesn't stop. Once I take my cursor off, the highlight persists. The only way I found to reset this was toggling the workspace icon on the sidebar on and off. But if I hovered my cursor once again, the highlight wouldn't stop if I took my cursor off. Does anyone have any idea on how to fix this?