I had this issue as well but it seemed to have fixed itself. I am on a PC and did a bunch of outstanding Windows 7 updates and it went away.
I also discovered that if you clicked on the fader and held the button (even if you didn’t move the fader) the audio would come back but as soon as you let go, it would disappear again. The project did not exhibit the same issue in 8.0.3. So strange but it seems to be fixed now.