Hi!
The problem there is that the default max-height for the filter boxes is set to ‘auto’, which means that it’s going to stretch as long as the list lasts. And since the search is in a fixed top position, there is no way to scroll down to those elements.
I believe the quickest solution is to change the max-height attribute to a pixel value like so: http://i.imgur.com/utzQfq0.png
Multi select for those is unfortunately not avaliable, only a single select layout.