The offhand attack of the Bearded Axe, the one where you hold the parry button while holding a Bearded Axe in your left hand, is bugged if you use a Short Sword in the right hand. It seems like the game registers a second attack everytime you attack with the offhand attack even though is only one strike at a time. Either there is an animation for the Short Sword that is not playing during the attack or the second hit is not supposed to be there.
Here's a clip so you can see what I mean.