I think it was a performance 'optimisation' to reduce the number of simultaneous sound effects playing, making it sound fairly awful as loud mechanical noises are totally silenced by the hum of one distant engine, etc. But aside from that, I've been continually getting the issue that fan noises do not resume after being silenced in this way. Demo tech attached - the lowest number of cluster missiles I could have to make this happen reliably. Works anchored or flying, etc. (Yet) another superficial little glitch during filming - I repeatly fell out the air and crashed because I was letting the fans on my "dropship" (attached too) totally spool down, to re-engage the sound effect after firing... I'm not sure of the overall specificity of the bug, but I think it happens with all fans/props, at least.