When looking at my assigned issues (https://bitbucket.org/dashboard/issues?section=assigned) I have exactly 26 issues. This seems to fit on one page, but the "prev" and "next" button are displayed next to the pagenumber. The "next" button has an href attribute "/dashboard/issues?section=assigned&page=<bound method DiggPage.next_page_number of <Page 1 of 1>>". The "prev" button has an similar href attribute.
Apparently, some debug data? Seems to make more sense that the "prev" and "next" buttons simply have no href, thus no action.