Sudden Audio silence; Audio sync

I have only 10 days left on the trial of Flash Pro. I am thinking about buying it, but I have been having some problems with the audio. First it was really in accurate, then it (when exported) messed up the syncopation. I was not exporting, and instead, recording the preview with my phone. Today, I was working on a piece and when I was about to show someone what I had gotten so far, the audio went silent. I have tried everything from my computer to removing the audio and placing it back in. However, nothing has worked. I have a limited time before I can get this small project done so I can see if I want to get it. Please help me. I don't want this poor sync and sudden muting of my audio to be something I have to deal with every time.