I had something odd happen to me. 

I had a city get taken without any warning or fight of any kind. I just saw it was taken, the name had been changed, and the champ and others I had parked there had been ejected. This might be a mechanic or something I don't understand...

Anyway, I claimed it back without a fight by just popping my stack back in the city. But once I did, the enchantments that were on the city before it was taken were totally bugged out. The little icons above the city were empty, but I couldn't apply any new enchantments. (the error said I could only have the same number of enchantments as essences. The spot has 2, but it was clearly empty.)

So I checked the enchantment lists on the govern screen, and the enchantments were there. But they were not having any effect, and the icons were not on the city badge. So I dispelled them. (it asked me if I wanted to dispell enchantment x on NULL, but it did sorta work)

I re-applied the enchantments and the game totally broke. I couldn't advance the turn or do anything.

A save and reload may have addressed that, though. It seems to be okay again.

So, I think I have a few bugs here, and perhaps a misunderstanding about mechanics. Why didn't the militia defend my city? Why did my stack get ejected? Where was the opposing army? Is this some spell I don't know about?

EDIT: I'm ashamed I forgot to mention that the game is EXCELLENT. I am having so much fun!