In flight, the only thing I found was using the mouse to move the throttle or speedbrake sometimes “unstuck” it - but not always unfortunately. And that’s if you are lucky that they are in view at the time, coz you can’t even pan the camera around. Also, wierdly, it seemed to lock out all controller input too - yoke, throttle quadrant etc.
Moral of the story is don’t press TAB! I guess if you are ALT-TABing to go to another window, make sure you don’t accidentally press TAB on its own.
EDIT - I also found that once it had happened once in a flight, the second or third time it became increasingly more difficult to “unlock” it by moving the throttle/speedbrake with the mouse