Thank you!
It took me a while to figure this one out – and it was more complicated as it looked. The issue boiled down to something very strange, where the “artist_category” taxonomy was not yet initialized at the time when the search was checking for the filter types. Because the taxonomy was reported by WordPress as non-existing, the code generating the styles for the drop-down was never executing.
I managed to resolve this with a bypass code edit, I replaced a piece of code in the plugin to ignore a warning, and proceed with the check nevertheless. This have resolved the problem.
I will make sure to include this change in the ucoming release too.
Because the search bar is hidden now, the order of the default ouptut may have changed, but you can still switch the settings and the results positions by using these shortcodes instead of the current:
[wpdreams_asp_settings id=4 element='div']
[wpdreams_ajaxsearchpro id=4]