www.mysite.com/?s=search+&post_type=product&dgwt_wcas=1

I am getting the same problem, please can you advise.

Same here. Tried removing [dgwt_wcas] with the following javascript, but I experienced more issues and dgwt_wcas was still there in the URL.

(function ($) {
    $(document).ready(function () {
		var $flags = $('[name="dgwt_wcas"]');
		
		if($flags.length){
		    $flags.remove();
		}
    });
})(jQuery);

Maybe this solution works for you.

Same issue for me. In some reason any dummy text in search field returns all products on search page, even when I have no results

https://prnt.sc/vlovbf

All of your cases should be independently checked. I suspect there is a conflict with other plugin or even your theme.

Checking plugins compatibility:

The best approach would be to deactivate plugins one by one and check if the issue still occurs after each deactivation. Especially focus on plugins related to product filtering.

Checking theme compatibility:
Try to switch your theme to e.g. Storefront, and check if the issue may be related to the theme.

If you want to debug it deeply, prepare a staging version of your website and contact us via https://ajaxsearch.pro/contact/

Best
Damian