Paging through scans should display thumbnail for page

[craigsapp]

With this example score: https://polish.musicsources.pl/en/lokalizacje/galeria/rekopisy/6089/5#nomenu

Here I am looking at page: 4/51:

When I click on the next-page icon, I see the new page as desired:

but the thumbnail for page 5/51 is not shown in the thumbnail list on the right. Ideally the thumbnail list would be updated so that page 5/51 would be shown as the bottom of the visible list. This would also be true when progressing backwards by page. In other words, the thumbnail for the current page should always be visible in the thumbnail list.