Cockpit Sound missing?

[ual763]

I seem to be missing pretty much all interior cockpit ambient sounds (with buses powered) on the ground.  I can hear switch sounds, warning sounds, external power cart, etc.  I thought nothing of it, until I suddenly heard them while recycling views quick.  Then, just as quick as they appeared, they disappeared again.  Not sure exactly how to reproduce other than cycling my exterior/interior views back and forth quickly on ChasePlane.