Not sure if this has been answered yet, however, I have just been trying to figure out vertical videos on my site, and your Width is set wider than the vertical. if you adjust the code to be the size you want vertically and horizontally it should get rid of the border. I haven't got mine precise yet... but I think this is the answer you were looking for.
width="800" height= "500" should read more like width="250" height="500"
How can I embed borderless vertical video files on Squarespace?
in Customize with code
Posted
Not sure if this has been answered yet, however, I have just been trying to figure out vertical videos on my site, and your Width is set wider than the vertical. if you adjust the code to be the size you want vertically and horizontally it should get rid of the border. I haven't got mine precise yet... but I think this is the answer you were looking for.
width="800" height= "500" should read more like width="250" height="500"
.