Jack on "[Plugin: Ultimate WP Query Search Filter] Getting searchresults 'uwpsfsearchtrg'"

I'm getting no search results. When I only select a combination of terms or with or without a search string, I always get the message Zoekresultaten voor 'uwpsfsearchtrg'
(searchresults for 'uwpsfsearchtrg')

http://www.dierbaardier.nl/

https://wordpress.org/plugins/ultimate-wp-query-search-filter/

All my settings for the three taxonomies are the same and like this:

http://pix.toile-libre.org/upload/original/1461931999.jpg
http://pix.toile-libre.org/upload/original/1461932072.jpg