IPB cuts transliterated urls. How to fix?

Question

IPB

Hey!
There is IPB 3.4.6. At first, there was a problem, which consisted in the fact that users with Russian logins could not log in to the forum (even considering that the login and password were entered correctly). At the same time, users with English logins were authorized normally. At the same time, the transliteration of urls worked as expected - the Russian topic name was completely transliterated.
In the process of solving the problem with Russian logins, the following changes were made to php.ini:
mbstring.language = Russian
mbstring.internal_encoding = UTF-8
mbstring.func_overload = 2
As a result, now Russian logins work without problems, but urls are transliterated or not completely , orare not transliterated at all . Tell me, in which direction to dig to fix this?