As you can see it appears as if the arrow thinks it is still being hovered on while I have moved on to the new tab. This only happens when you hover over the arrow and move to the right. A few pixels further to the right of where my mouse is at in the screenshot the hover state will go away and hover the active tab as it should.
To make matters even worse, whenever this happens and I want to click on the tab I am actually hovering over (in this case the active tab) the drop-down is triggered of the arrow it believes I am hovering on (the voted tab)! :O
On Vivaldi, 1.4.589.11 (Stable channel) (64-bit) Ubuntu 16.04
- FireFox 49.0.2
- Chrome 53.0.2785.143 (Official Build) (64-bit)