This might be a dark mode thing:
open Library
click on Series to group resources by Series
Click on the + tab to open a new tab
Go back to Library tab, click on one of the series to open it
...at this point, the series being highlighted as you scroll up and down through the list of series is out of sync with where your mouse cursor is. It pretty much stays that way until you click Title to remove Series groupings.
I have seen this happen in other ways too, this is just one example.
