Plugin works erroneously

Hello,

I have used the plugin on http://www.fmcareandsupport.co.uk and in particular on all pages in the What we do section. It regularly fails to show any results but when I try a few minutes later, sometimes it works, sometimes it won’t. I’ve checked each page and the code and setup of the plugin are correct.

Thank you

https://ww.wp.xz.cn/plugins/ultimate-wp-query-search-filter/