I just ran into an odd bug. I'm running Mac OS Sierra. I had about 100 Renown saved up, and a Warrior that had the needed kills for his first promotion that I was waiting on (I was trying to maintain the flexibility to battle the occasional newbie who comes in). Here's what I did:
1. Buy new space in roster since it was full
2. Hire new warrior
3. Promote existing warrior
When I did that, BOTH the new warrior and the old one were promoted (to the same type), given the same name, same number of kills, etc. I apparently have discovered Viking cloning.
I've also noticed that the Steam overlay NEVER works. It's a pity, because I'm considering tossing a few bucks your way, but I can't see a way to do it.