Intersecting dungeons: spawner replaced by cobblestone

How to reproduce

1. Create a customized world with the seed

   3097946827751441825
   

   and default settings except dungeon count which should be 100

2. 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.