Whenever I add ? with many characters after my website url I get the same page; the url is the same along with the search queries. 
domain.com/anypage/?s=700chars returns domain/anypage/?s=700chars but encoded: spaces become %20.
This is ruining my search queries: instead of showing results it shows the same page.
I tried it on another server and it returns results. To test it I put a working site on the server with a non-working site, and it stopped searching correctly.
I strongly suspects it's the server but why?
 
    