I captured a Magnar city this afternoon, it had 0 grain, 0 material and 0 essence !!!
Share save or it didn't happen 
Really it helps because the developers can check out all the tiny details about the map, and the area around the city, etc.
Also, I had my sovereign in another Magnar city, just captured, with its complete army, and ONE Magnar unit (pikemen) attacked the city alone!!! I think they were in a hurry to end their lives
That sounds rather odd, good of you posting it here 
A post here in case you need to post bugs "more effectively": https://forums.elementalgame.com/415301
It includes information about the Debug.err file, and tells about stuff like www.dropbox.com which is a program which you can use to share save files.
Sincerely
~ Kongdej
