Flash? Yes, probably. But it moved the entire window content, not just the video frame.
Latest posts made by jonhy05
RE: Content stays out of window after moving a single tab to another window.Opera for Windows
Content stays out of window after moving a single tab to another window.Opera for Windows
This is hard to explain so I'll let a picture do the talking:
All this happened when I have one window with one tab on each monitor, decided to pull the tab from the right (the one with the video), to the left window and voilá.
Couldn't replicate it.