View Columns button dropdown menu disappears when using browser's up/down scrollbar

On ND version of 11.4, when using GBNG, instructor with many grade items has decided to hide a couple of categories in his spreadsheet view to make navigating his spreadsheet more manageable. He attempts to scroll down the list of all his grade items using the Hide/Show button in 11.4 (now renamed to View Columns in 12) but runs into a problem. 

He clicks the Hide/Show button in 11.4, which opens a dropdown listing of all grade items. He can't immediately see all the grade items in that list (which is fine - it's a long list). He then attempts to scroll down the list using the browser's scroll bar. As soon as he clicks off the dropdown list onto the scroll bar, the dropdown list disappears.

On qa2, when the instructor clicks off the View Columns dropdown menu, it remains while he scrolls down, but as soon as he clicks off of the scrollbar, the menu disappears (see video).