[Plugin: WP-PageNavi] Problem with no index.php on reverse paging

Hey
I don’t use the index.php on this domain and I’m using wp-pagenavi on my search results page.
The paging works fine when you search something, I mean, you can navigate to page 2,3,4,…9 etc.
But if I navigate to page 2, and go back to the first page, the link to page two kills the index.php from the first page, and add it twice to the following pages like index.php/index.php/page/2 which gives me a not found page.
How can I solve this?
Thanks!
The page can be seen here https://www.duqueestrada.adv.br/index.php?s=vasp&=buscar go to page 2, then get back to page 1 and try to navigate to page 2 again.