This is a long time I am seeing this problem and it's not yet resolved. Please do something Pangolin... it already made me shameful in front of my audience 
To reproduce it :
- Go to Timeline, open any show with a .WAV as media
- You see the waveform, all is ok
- Go to the Grid
- Play any other cue, then stop it (ESC key)
- Go back to timeline
- You see now a beautiful error cross on the Media file !! And of course, no sound when playing the show.

To reproduce it :
- Go to Timeline, open any show with a .WAV as media
- You see the waveform, all is ok
- Go to the Grid
- Play any other cue, then stop it (ESC key)
- Go back to timeline
- You see now a beautiful error cross on the Media file !! And of course, no sound when playing the show.