I'm assuming that you made the buttons into a data list? The most common cause of problems like this that I have seen is in not including the scrollbar in the data list. Ideally, you'll want to create the data list with the scrollbar in the first place, but you can add it later - simply cut the scrollbar (Edit -> Cut), then double-click the data list component to edit in place and paste (Edit -> Paste). Once you do this, the scrollbar should work fine.
If I place buttons in a datalist, they cannot be used to command videos.
It seems I have a good solution by moving the 2 groups of buttons with arrows (up down left right) and placing 2 masks to make the buttons slide under at several places.
I'll show my web site when finished.