This is my redirection URL (this is redirection to Polish online payment system):
https://sklep.przelewy24.pl/zakup.php?z24_id_sprzedawcy=17676&z24_kwota=5000&z24_currency=pln&z24_nazwa=nowy+cz%B3onek&z24_return_url=https%3A%2F%2Fptgo.pl&z24_language=pl&k24_kraj=PL&z24_crc=d47e4cd8&
Try to redirect from Forminator to this url and see what url has been loaded.
Note the z24_name parameter (there is a Polish letter “?”) and the z24_return_url parameter (this won’t work at all without %-encoded characters). When redirected to this url, %-encoded characters are completely removed.
