Beatdown attack speed

[twin depot]

I believe that is just it activating, the buff only activates when zombies have certain injury knockdown buffs, just because they are on the floor or ragdolled does not mean it activates. As for the incredibly fast speed I believe its intentional as the attack speed buff is set to be able to be stacked

[teal cairn]

Intended to stack, OIP is correct with certain knockdowns.

And yes, you do eventually punch that fast that it sounds like your arm breaks which I find highly amusing