Submit calles search page with no parameters

No matter what search parameters are, a taxonomy, a category etc. on submit it just goes to http://www.domain.com/search which returns 404 not found error.
Only on keyword search sumbit button gives http://www.domain.com/search/keyword and shows results.

http://studiopdev.com/demo-labras/

I used this plugin before and it worked perfectly on the same theme/plugin configuration. Maybe update of wordpress or something corupted the engine or something…

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