The boundaries of structures like witch huts, nether fortresses, mineshafts, desert/jungle temples and strongholds don't get saved with the world file.
That's an issue because Minecraft keeps getting updates which sometimes might change the shape or the position of the structures.
When ever that happens mobs which only spawn inside the structures won't spawn there anymore.
The last time we saw that happening was the change of nether fortresses in 1.6.
By adding the chests to it the the random object which is used for generation was changed which caused the fortresses to generate in a different shape.
Therefor wither skeletons and blazes don't spawn in old fortresses anymore.
This post is covering this issue: https://mojang.atlassian.net/browse/MC-15547
Since the structures aren't saved it's impossible to fix the nether fortress issue. Either the old or the new fortresses will be broken.
I decided to post this issue even though the nether fortress issue is related to the same cause because I want to suggest that the mistake isn't made again for neither for nether fortresses nor for other structures.
The other structures should be mentioned in this context since 1.7 is a biome update and changes to the structures are not unlikely.
Linked issues
duplicates 1
Comments 7
MC-15547 is still open.
@Tails Yes, MC-15547 is still opened. But it only is about the nether fortress bug.
This one is suggesting to fix it for all structures so that something like this wouldn't happen again.
So if you mark it as duplicate please add the information about other structues to the other post.
It's not quite the same bug. Or is there anything about witch huts, mineshafts or strongholds in MC-15547?
MC-15547 does only include nether fortresses. Please add the part about other structures as well as the suggestion for a fix to the other bugpost or reopen this one, so that this bug can get fixed, so that we don't get the same unfixable problem for other structures with the next update!
They aren't the same bug. That was how the world doesn't KEEP the data; this is how it doesnt save it and if the algorithem changes, everything breaks.
Mojang, please fix this before 1.7!