Unable to scroll Subject Areas with Union

Summary:

When trying to use the "Combine results based on union intersection and difference operations" I'm unable to scroll past the initial list of Subject Areas to the lower list.

Content (required):

When selecting a subject area it loads an initial list of Subject areas that will expand if you reach the bottom. Screenshots below:

• In this screenshot you can see the list of Subject Areas scrolled to the bottom before it manages to expand from refreshing the list with additional options.

• Here, you can see the list expanding to include additional options.

• When trying to use the set operators it will pop up the same box to choose your subject area.