I figure I need to remind readers what is happening - and to make sure this thread stays active.
In attempting to resolve this problem, I made it through to Level 2 technical support where they remotely accessed my computer. They were at a loss to correct it. Suggestions even included I use the "clean audio" function - to modify hardware vs software rendering, and included the old standby update drivers, etc.
I am able to replicate the problem on a Win 8.1 machine, Windows 10, and Windows 7. All have the poor audio where the audio edited is greater than 15 or so minutes. This occurs on differing hardware (one is my macbook on duel boot).
I had attempted so many fixes they had to reset my permitted number of installs.
After a great deal of work, I have managed to discover how the problem can be replicated and reviewed:
1) Change the Proxy Files location to an easy to get to folder so you can detect when the proxy files have completed rendering.
2) I delete all proxy files.
3) When a video file is first loaded - playback is fine. (Rendering at this point will result in corrupt audio in the final result).
4) For every video edit, VideoWave creates an audio proxy file in the Proxy Files location. When the proxy file is finished I save the production - enter a new production, then reload the saved production. This will then cause VideoWave to access the proxy file. If you listen to the proxy file in a different program, like VLC, the audio is corrupted and distorted.
5) Once reloaded - the audio for the file beyond around 7-10 minutes is corrupted.
6) Even more interesting is that if I delete the proxy file and reload the production, the sound is fine - until the proxy file is created and the production reloaded.
7) Once reloaded the audio is once again corrupt.
There is something wrong in how Roxio VideoWave transcodes the audio portion of the video files improperly. I believe the settings they pass to ffmpeg are incorrect, but are hardcoded into VideoWave.
I have used many different file formats and the result is the same.