I am using core joomla 3.9 and Sh404SEF component with Purity III. The problem does not occur with core Joomla templates.
The pagination is broken on e.g. https://hitradio.com.na/aktuelles/nachrichten/
At the end of the content e.g. page 2 has the URL /aktuelles/nachrichten/page-1, page 3 as well, page 4+5 have /page-2, pages 6,7 and 8 lead to /page-3, and actually the "end" lead to /page-268, which is actually page 650 and not the last one.
Consequently, it is not possible to reach the pages as SH404SEF in combination with Purity III allocates pages that are non-existent, rather than using the normal start=20 etc.
Pagination errors with Sh404SEF are frequently mentioned in different Forums, but mostly related to FlexiContent, which is not used on this site.