I just ran into a similar problem with the living club. It seems that at level 2 the damage die increases with each passing tick. Additionally, while in a menu, you can un-select and re-select the weapon to watch the damage increase. This was fun until I encountered a Scrag that one shot me with over 120 damage. I know Scrags don't really do that much damage. Further tests indicate that all natural attacks had increased exponentially. Hope it helps!