That's.... really darn weird. I'll check the pertinent files when I get home tough I really bloody doubt somehow tengrii got changed for suomenusko, that's not something you do by accident :blink: Just so we're clear, you're saying the mongol characters appear as finnic? What about the unlanded mongol characters?
I have checked the Golden Horde's vassals and courtiers. Oddly there are some unlanded courtiers who are Tengri (including the Kahn's wife of all things) as well as the Turkish Sunni they took from the Seijuks, but the vassals and even some unlanded courtiers (along with the Kahn's children) are indeed Finnic religion. I also checked the Ilkahnate and they have no Finnic characters of their own, it's either Tengri or Sunni.
So... yeah, I dunno what's going on. Not that I'm complaining, but having the Mongols go to war with each other instantly is a bit unbalanced I'd say