Upon game start, some nomads would be occupying a wilderness province like it was a siege, and nomads would go crazy and fracture into nomadic OPM's ... short, it was a mess. This is most likely due to the old teams of the mod never using the historical_nomad = yes things with history and just giving nomadic gov type to easterling cultural group. Also, many instances of wrong gov type for nomadic vassals contributed to the mess as well.
They will be figured out eventually, but for now its much nicer than it was.