I isolated this Problem to AddonSkins and Domins.
I downloaded both Addon freshly and didnt load any profiles.
I tryed to fix Dominos settings, but couldn't find any solution.
From my understanding it's a Problem with AddOnSkins.
The FullwindowCooldown is shown as long as the actionbar is visible from dominos.
e.g. if i the action bar is on faded opacity the cooldown just shows when i hover over the bar.

A fix would be super nice!

I checked this and it is working for me.. So maybe you are out of date on AddOnSkins. I haven't touched anything either for Dominos are awhile.