Desperate for solution to pagination problem

What’s happening is:

When a term is searched, the results are returned, but when you click page 2 or any other page beyond 1, you get “nothing found.” NOT a 404, just “nothing found.”

I think the problem is:

The new url looks like this:

https://www.site.com/?s=tile/page/2

I did a few tests and figured out that if the url is printed in the reverse:

https://www.site.com/page/2/?s=tile

page 2 and subsequent pages show up just fine.

What I can’t figure out is where to change how this is output.

This is a custom theme, and though I know the best thing to do is contact the developer, said developer hasn’t gotten back to me on any of the issues with it since July, so I’m wondering if someone here can point me in the right direction as now it’s getting urgent.

Thanks for any and all help.