Broken 'Back to' Feature

When you are on an item page in someone's gallery, there is a link "Back to [series title]" and should put you back on the page you were on when you clicked on the artwork. However, this the formula for figuring out what page to put you on doesn't seem to take into account hidden artwork. So, for instance, if you are on page 2 of a specific series artwork and click on an item, and there is a lot of hidden artwork, when you click on the back to link, it might put you on page 3 or 4. Sometimes these pages are nonexistent, at least nothing appears on them.