Wither Skeleton are NOT Spawning

They spawn but they're rarer on pe than console and java

Theyre supposed to spawn in nether fortresses and none are spawning from the* 5* I've been too.

Affects 1.0.6.0; I'm sure they spawned in the same nether fortress, but in previous updates. But now they don't spawn at all, even after walking around the fortress for about 30 minutes in hard difficulty; this also affects blazes, now they only spawn from spawners.

Resolving as cannot reproduce as of 1.0.6.0.