[Koha] Nonfiling characters and sorting

I'm not sure if it's just our catalogue, so would ask for confirmation (or denial) by others before exploring further. In both OPAC and staff interface, the "sort" drop-down defaults to 'relevance', but for longer pages users and staff sort by 'title A-Z'. Normally a biblio with a 245 second indicator set to, say, 4 drops 'the ' (3 chars and space), but we are finding that it does *not* drop German articles such as 'der ' and 'die ' Example: <http://opac.navalmarinearchive.com/cgi-bin/koha/opac-search.pl?idx=au&q=nowarra&sort_by=title_az:> which has both English and German usage. Has anyone else noticed this? Thanks -- Paul