I have looked at the configuration and made a few minor changes to redirect to the correct URL, as I see you use a custom permalink structure.
However this did not help, as I believe there might be another plugin or the theme simply overriding the search results, I'm not sure – it can be both actually. If there is any tempering with the results within the theme files, like doing a query_posts(..) call within the search handler file or anything similar, that would explain it.
Let me know if you know anything about that.
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