I'm having the same problem.
I fly an F-4E, and when I put it into active pose for practice and press a button,
it behaves so badly that it almost crashes when I release the pause.
The most likely cause is using the automatic attitude control.
The pitch up trim keeps moving while it's paused.
The autopilot tries to correct the attitude, but the aircraft doesn't move because it's paused.
I think it's repeating the same operation to do that.
Try looking at the aircraft's instruments once while it's in active pause.
*Sorry if it's not autopilot.
Another problem is that when you start a mission in the air,
the engine starts at idle.
So if you don't increase the throttle, it will crash.
Is there anything I can do about this?