Nagot gick Fel! Error Code List?

[Edratman]

I think I remember the circumstances when I got it. Lets say 50 to 60% sure.

I think you are using a mod and have a unique commander assigned to a non unique position. Most likely as a commander in province defense. Most of the time when it happens to me it is when my keyboard typed the wrong number. It usually works until you have to defend 2 provinces on the same turn.