Hi,
I’m having the same problem with a splash image. This is the opening splash image, not the javascript one at the end. It’s as if the image width (not the height) is compressed and left justified, letting the dark gray background peak through on the right.
This is clearly not a CSS image size restriction, because I test shrunk my player size from 640×360 to 64×32 and, even though tiny, I can still discern the splash image distortion.
Note that the video properly fills the player.