Hi,
Thank you very much for the details, it helps a lot!
From the request body it seems like the search sees as if the language is still english, as for some reason the “en” language code is printed to the search bar.
I suspect this might be something to do with the block cache – as if the cached “english” version of the plugin block is printed to the page with the original “en” langauage code.
Can you please try to replace the search block with a shortcode block and use this shortcode with it: [wd_asp id=1]
Also, please make sure to clear the page cache as well. If all goes well, that should re-render the output correctly for each language with the correct language code string in the search bar.