This happened to me two times in a row now, previous patch and now the current one. Others have reported the same issue on the forum.
I kill an infected with a melee weapon (machete and pointy stick) and after I can not walk normal any more, very choppy, almost as if a Z is hanging on my leg :) I can sprint normally but walking gets bugged. There seems to be nothing I can do to get to a normal walking state (crouching, prone, jump)