Audio stop

I added 2 video clip with audio file. Everything is ok can play the track and everything work fine. After editing audio track or move audio track on the time line I lost audio, can't hear anymore any audio track.

The audio track level meter show activity but the buss don't show level activity. When i double clic the audio track I can hear it but the buss still show no audio level. After reboot Davinci it is working fine but as soon I move an audio track I loose audio and bus still showing no activity.

Any one as a clue, Regards
Clement