What's happening is when I enter the Nether for the first time and I come upon a fortress the Wither Skeletons are able to spawn, however, when I exit the nether or quit the game and reload, the Wither Skeletons no longer spawn and seem to be spawning Ghasts instead.

I am very aware of all the block levels that Wither Skeletons are able to spawn at for each specific structure that makes up a nether fortress. I'm not missing them because I have some ignorance of the game's spawning mechanics. They're actually not there.

Many of the Ghasts are stuck in the fortress hallways and other structures. This happens frequently. Where normal Ghast rates are everywhere else around the Nether, if I'm at a fortress that has been loaded for a second time, I'm often fighting 4-8 Ghasts at any time. And it really never stops. The only time the Ghast rate is at normal is the first time I load up a fortress and Wither Skeletons are there. To me, with so many Ghasts spawning around the fortress exactly in all the points where the Wither Skeletons normally spawn, something is happening where the game is spawning Ghasts instead of wither skeletons. Brand new prot IV unbreaking III armor is down to half durability just from a couple hours of constantly fighting off 4-8 ghasts at Nether Fortresses. I don't think most people are repairing their prot IV/unbreakingIII diamond armor every couple of hours. Something's amiss.

This has happened on every world I've generated in the game. I've exported and imported, I've uninstalled and reinstalled the game, I've tried changing the difficulty levels in game, just about any little nuance I could think of that might be causing this to happen. I'm aware of where the game files are on my system but I have not touched anything.

Beacons are something I've been looking forward to for a long time. Please help me out with this bug.