So now everything works, navigation will no longer freeze.

Just change the phone's main language to English.
Thanks for
Steve_M and
NetworkMan.

However, as I found out, this bug has been around for a long time and it is very surprising that it has not been resolved yet.

I didn't know about this error until now.
Now I changed English to UK and drove a slightly longer route. All three navigations work OK, only Organic Maps' voice navigation stutters (it skips the first word). But that doesn't bother me at all, because I only use Mapy.com.
And the second thing is, I don't mind that the phone is now in English - because I pulled my old spare phone out of the drawer just for navigation.
And that's the
advantage of Mapy.com - that I can have several devices for one profile, where I will always have the same routes, points, etc.
And there is one more advantage to Mapy.com: not only can the voice navigation be in a language other than English, but the application language can also be set to a language other than English.
With the aforementioned HERE WeGo and Organic Maps, the application language cannot be changed; it is automatically taken from the phone's default language.