When you open up a block UI or your inventory even when your mouse is on a slot either boing the bottom or top the top left slot is always highlighted and you have to remember to move the mouse to update the selector. Even if they mouse it on the item you want to click on it the item that is highlighted on the top left when you open the UI it would let you select the item your mouse is on. I am not sure if this affects other platforms. It has been happening for around 3 months.