Raster of Guk PH's.
 

Second time i've come across this bug where the PH for Raster of Guk will not despawn, but will spawn another mob right on top of them. first time I saw it there were 9 PH's there. Second time 5 PH's on his spawn point, but I have seen it work properly before (unless I just happened to arrive after someone else left).

Fixed, pending update.