It's just a video/audio sync issue... like an old kung fu movie (KungFu Craig). I would have thought it was just the older imac I am using (still will ProPresenter4), but one of our guys with Pro5 is having the issue, and one of the guys with Pro6 is having the issue.
For me it started the series during Christmas, I believe. I have found some ways to alleviate the problem, but it is still just a hair off, and distracting when you pick up on it.
I'm going to a new imac and Pro6 soon, but it seems to be a little more involved than that.