Can't do chieftain battle with Tamurkhan

I have met all the criteria, however when I Try to teleport to the battle the game says I can't as he is currently garrisoned in a town. He is not, he's in an army on the campaign map. I tried removing him from the army and reinserting and still no good.

Has anyone else had this problem? Is there a fix?

Thanks

EDIT: It's Tamurkhans army that the game bases eligibility off of, not the army the particular chieftain is in. So once I put Tammy in normal stance not in a settlement I can now do the battles.