There are known issues with Blackmagic devices and audio sync problems. If you're experiencing audio sync problems with your device you should contact Blackmagic directly to help resolve the problem. Our technicians have reached out to the company regarding this problem and they have suggested that plugins and / or updates are needed to help resolve the issue.
For more info visit:
https://www.google.com/#q=blackmagic+audio+sync+problem
More info for Intensity Shuttle, specifically:
https://www.google.com/#q=blackmagic+shuttle+audio+sync+problem