Zombie pigmen

Zombie pigmen randomly attack not only myself, but other members in my minecraft world. Not all of them attack at the same time either, only one or two at a time. So this clearly is NOT caused by them being agro'd!!! This happened in the last update (which I thought you guys would fix by now) and seems to be even worse after the update today! I have been chased almost every time I walk through the nether. Even after a 5 min cool-down and reloading the world! FIX THIS PLEASE!

 

I figured I would add this: you cannot place the top half of a slab on the underside of a block. It places a whole block, instead of a half slab. This did not happen until the update today!