Really weird bug this. I was going for a piece of fertile land to found a city there. I spot Karavox near it, his card saying he's heading for Aredriewe (his capital). A bit odd since he is directed towards the fertile land. Anyway, I found a new city and go to a hut nearby. When I start heading back, I notice that my newly founded city is called Aredriewe and is owned by Krax (no units nearby so it wasn't captured)! When I enter the city my own city name comes back and... Karavox capital is destroyed!

The save KU3 is where I just found that the Krax capitol was destroyed. KU20 is the autosave, right before I founded my new city.

It does not seem to happen again if I keep playing the autosave.

Saves and debug