When fighting against zombies, sometimes you will be put into a bugged state,
Even when putting away the weapon, the character moves as slow as if the weapon is still out + raised, the only thing that can fix this bugged state is to raise a weapon (or fists) and lower it again.
when a zombies hits you when you are mid-swing (at least this happens mostly when i get hit by zombies mid swing1) get a two-handed weapon, might be unrelated)
It happend to me with the followingand attack a zombie (might work with any weapons:)
Pickaxe2) get hit by the zombie (mid swing, maybe even without mid-swing hit)
Handaxe3) put away the weapon
Fireaxe
Pitchfork
4) notice your character moving very weird, you seem to be running with normal speed, but you will be pushed back constantly,
as if you are running against very strong gushes of wind