This is truly wierd!
1080p25 HD project. Drop a 1:1 pixel 1920x1080 PSD file onto the T/L. All looks as it should, going good.
Comp 1920x1080 video onto an upper track. I can move that video several pixels outside the frame. No, I don't mean it's being masked by the frame, it's NOT being masked by the frame. So the preview window has now got a bump out the side of it several pixels wide! To explain it another way, my preview window is now effectively 1922x1080.
What's causing this is the video has a mask applied on an upper track, disable the mask and the video shifts back to inside the frame.
Bob.