Thanks for the screencast. This behavior is a side effect of the "new" embed code for TubePress Express. Instead of a fixed-height <iframe>, the embed code injects a flexible <iframe> that readjusts its size as needed. Initially that injected <iframe> has a height of zero, which causes the "jumpiness" that you see when TubePress resizes it.
I've just published a minor change which I think makes it far less noticeable - maybe even imperceptible. Could you recheck your site to see if it looks any better? Basically all I did was start the <iframe> height at 500px, which pushes it below the bottom edge of the browser.
Let me know - thanks!Go to the full post