I think I ran into this problem too, when I host the game in my PC everyone travels to the map, when I host the game on my brother’s PC the same, but when I host the game on my less powered notebook I and my brother keep stuck in the loading.
So my question is, if the bug has been reported in Jun 16, why its still happening now in Sep 21?
Edit1: It seems that the unreleased 5.1 addresses this, the function HasClientLoadedCurrentWorld check return is now
return (Connection->GetClientWorldPackageName() == GetWorld()->GetOutermost()->GetFName());