When embedding video files (i.e. from YouTube), the Highslide script displays scroll bars in the pop up window (see attached image). Those scroll bars need to be set to disabled and the window to be resized automatically, depending on the additional video description length (alternatively remove the entire description block and don't display at all)
The issue only displays in embedded videos - not in uploaded videos or images (although using the same Highslide script).
I can provide assistance and any file or access to the site however I am unable to resolve this issue by myself due to insufficient PHP/JAVA/CSS knowledge.
The Highslide script is being run from inside SMF2.0 (Simple Machine Forum) via AEVA Gallery - all of those mainly use PHP and CSS