I have customized the Story Map Series according to the source. I have 18 entries in my map series, and the accordian panel does not scroll to the entry with the base code. I added these two lines to scroll to the entry, but it is not quite working completely.
//with the accordion theme, if there are more entries
//than fit on a single screen, this scrolls to the active entry
var entries = document.getElementsByClassName('entry');
entries[index].scrollIntoView(true);
On a click on the feature (i.e. entry index >13), the panel does scroll to make the entry visible, but not at the top. On a second click on the feature, the panel scrolls to have that entry at the top. Putting scrollIntoView in there twice does not help. Here is a video clip.
This scrolling issue was a bug that was fixed in the September 2018 revision of the Story Map Series code.