Bill.

My own personal halfbaked theory is that the vision/sound sync maybe slipping slightly and that the camera has a bit of a shakehand after a long roll to set things to rights as both cams have done this to me during long takes on music gigs I think from vague memory at about 12 minutes. It has not happened enough times to vex me.

Cineform's Aspect HD used to sometimes insert a split scene on these when converting but it seems to have gone away lately.