Here's what I noticed: When you spam left mouse button whilst using a melee weapon (mainly occurres with the fire axe) the attack will look like as if its being swung a thousand times more than it has to. It looks like your hitting something and mixing it with your axe as you stick it on your enemy and then shaking it with a back and forth motion. To test it you can take a fire axe and spam mouse1 against a zombie but I may have exaggerated.