I am on a solo world and just finished day 28. The hitching is HORRIBLE! It happens every couple minutes, causing me to miss swings with my sledge or if I am trying to 'parkour' I end up falling and break my leg.
It seems that anytime something is loaded such as loot in ANY container (player storage included) or when a new group of zombies is either spawned or 'activated'.
I will walk into a room and see some sleepers and shoot one to pull them into a choke point but when I do that I get several bad hitches that will clear up by the time they reach me. But if I do this with melee I will get hit several times before the hitching is done.
EDIT: This is in my solo world! In my three player world I just assumed it is the internet but I guess that is not the case.