Search option not working

Hi, I am creating 2 search fields using this plugin, one for search by size and 2nd one is search by brand. Now my problem is “search by size” this one working properly but when I click on “search by brand” and try to search then it’ll be auto-redirect “search by size” search field. For more better understand go to this page: https://navdisenyo.com/demo/ and check “search by brand”.

Please help me asap and let me know how I can fix it?

The page I need help with: [log in to see the link]