(v16, linux)
This is probably known. So just in case...
When you point the mouse on top of one of the UI elements and a tooltip is shown before ending the turn prior an enemy is about to act, the tooltip will persist on the screen till the next ally's turn.
I would expect the tooltip disappears for the enemy's turns.
Additionally (suggestion): is there any reason why the bottom indicator of AP points stays in the view while rest of the interface is hidden?