Mouscursor leaves game screen, making the game unplayable.

After upgrading to 1.21.50 the mouse cursor leaves the game screen. 

So after clicking, the game will "pause" (that is, the mobs will kill you before you are able to get the mousecursor back in sync and the game controls back.

This did not happen before the update to 1.21.50 

The game is now unplayable.