War against tribes is so fucking bugged

So after my Mongolia Great Khan game I decided to do a chill Norway exodus to pick up Let it Go (no way in hell I'll do Norwegian Wood). But the buggy state of war against the tribes inn North America is driving me up the wall.

1) Why can the AI take provinces out of coring range?

2) Why does a tribe being annexed by the AI not move them to a neighbouring province?

3) WHY CAN THE AI ANNEX OPM TRIBES THAT I OCCUPY?!?!?!