Sometimes the wither skeleton just drops the drop of the normal skeleton.

I know because it drops arrows and they are not suppose to.

This is my config:

http://pastebin.com/UCwy4iuc

i did it like this:

" WitherSkeleton:
Coin_Minimum: 1.0
Coin_Maximum: 3.0
Coin_Percent: 50.0
Drops:
- coal:1:75
- bone:2:75
- 397.1:1-1: 100:"

(BE aware there is a apce between the : and 100 because of emojis
(put the wither skull on a 100% drop change for testing)
But this works. it drops witherskulls

its a temp fix for now :P