I’m playing the game on a 4k tv at 1080P window mode. I have constant trouble with losing mouse focus when in combat. It’s like the mouse icon is still moving around but invisible since I’m in combat, but it still has the button active for it outside of the game window so when it moves outside the window and I click to attack it clicks on the desktop and the game is no longer the active window.
Edit: I noticed it happens outside of combat as well. It only happens when I move my mouse down and click. Left/right/up don’t do it.