How to reproduce
Create a customized world with the seed
3097946827751441825
and default settings except dungeon count which should be 100
Use the following teleport command
/tp @s -2611.29 32.13 3316.08 296.21 20.59
Code analysis
Based on 1.11 decompiled using MCP 9.35 rc1
The method net.minecraft.world.gen.feature.WorldGenDungeons.generate(World, Random, BlockPos)
only makes sure that it does not replace chests, but does not test for mob spawners.
Linked issues
relates to
Attachments
Comments
Yes, the same bug occurs also with the same seed with a freshly generated world in Minecraft 1.9.4, without world download, using Dungeon Count 100.
Like I said, the world download includes non-default world generation options. With default world generation settings, there is no double dungeon at this location.
I managed to reproduce this on 1.13.2.
Seed: 3097946827751441825
Double dungeon XYZ: -2607 31 3319
Observe that the second spawner has been replaced with cobblestone.
Important note: this dungeon does not generate as a double dungeon if you directly /tp to the coordinates. I can verify the double dungeon spawns on a fresh world when teleporting to -2572 31 3275 and then moving to the dungeon coordinates specified above. There seems to be a quirk where teleporting directly into the ungenerated chunk can influence the dungeon generation.
Found one broken spawner in 20w22a from a stronghold. It looks like this should be reopened.

@@unknown, since this involves a stronghold it might be a separate (but related) issue. Could you please create a separate report and provide seed, coordinates and (if necessary) world generation options in text form there?
Yeah I’ll create a separate ticket for a different dungeon bug.
I made a ticket MC-190568 for the stronghold destroying the spawner.

This bug was either not actually fixed in 20w22a, or else it was reintroduced in a later version. Please see MC-199953 for a seed and coordinates that reproduce this bug in 1.16.3.
Does this occur without the world download but with the same seed?