Hyperlink Click event does not fire when inside a ScrollViewer that has scrolled once

I have solved the problem with the hyperlink Click event. This had nothing to do with the ScrollViewer being scrolled; the problem was that the first page in a book chapter is a RichTextBlock and the subsequent pages are RichTextBlockOverflows.

I was treating the RTB differently from the overflows in terms of which events were enabled, and this was causing the Hyperlinks on the overflows to not fire.