I had the same problems with the audio/video sync. At first, I could only digitize 20 minutes at a time, then finally 1 minute at a time would not work after the last product update. What I had to do was uninstall the latest version and go back to version Decklink 7.4. There I have no problems with sync at all. I hope this works for you as well. The interface is not fancy but it works.