Well this must be a hit & miss thing regarding the sound not working in films. It may be dependent on each individuals sound settings in game possibly since I can hear all sounds except flaps moving up or down, and wind/stress sounds for my aircraft, and I can hear the opponents planes engines in my films I have recorded the past several weeks & patches
2 patches ago, I did have it where sound would drop out completely in game, but if I alt-tabbed out and came back in the sound immediately came back ( this happened about 4 times total ) but has not happened since.....