this does not solve the problem,
but next time press the alt key twice.
tell us what happens.
I tried pressing the alt key twice in CFS2. It paused the play but didn't stop the inappropriate feedback. Hitting the P (pause) key does the trick in CFS2. I haven't tried it yet in CFS1, but I will and will let you know.
Firng rockets occsionally starts the machine gut stutter feedback in CFS, but unlike when it starts by firing the machine guns, pressing the G (gear) key twice has no effect. Mouse clicking off the playing screen does stop it.