Program: 34797
Project: 34797
Buggy source:
@Override public boolean addComponentParts(World world,Random rand,StructureBoundingBox bb){
  int centerX=sizeX >> 1, centerZ=sizeZ >> 1;
  if (!isSetup) {
    structure=new LargeStructureWorld(this);
    Random consistentRand=new Random(((startX / 9) * 238504L + (startZ / 9) * 10058432215L) ^ world.getWorldInfo().getSeed());
    islandBottomY=6 + consistentRand.nextInt(25);
    biome=IslandBiomeBase.pickRandomBiome(consistentRand);
    biomeData=biome.generateData(consistentRand);
    noiseGen1=new NoiseGeneratorOctaves(consistentRand,16);
    noiseGen2=new NoiseGeneratorOctaves(consistentRand,16);
    noiseGen3=new NoiseGeneratorOctaves(consistentRand,8);
    noiseGen4=new NoiseGeneratorOctaves(consistentRand,10);
    noiseGen5=new NoiseGeneratorOctaves(consistentRand,16);
    biome.prepareDecoration(biomeData);
    Block[] blocks;
    int chunkX, chunkZ, blockStartX, blockStartZ, xInChunk, zInChunk, xx, zz;
    float yMp=0.66F * biome.getIslandMassHeightMultiplier();
    TimeMeasurement.start("String_Node_Str");
    for (chunkX=0; chunkX < 13; chunkX++) {
      for (chunkZ=0; chunkZ < 13; chunkZ++) {
        blockStartX=chunkX * 16;
        blockStartZ=chunkZ * 16;
        blocks=new Block[32768];
        generateTerrain(chunkX - 6,chunkZ - 6,blocks);
        for (xInChunk=0; xInChunk < 16; ++xInChunk) {
          for (zInChunk=0; zInChunk < 16; ++zInChunk) {
            xx=blockStartX + xInChunk;
            zz=blockStartZ + zInChunk;
            for (int yy=0; yy < 128; ++yy) {
              Block block=blocks[xInChunk << 11 | zInChunk << 7 | yy];
              if (block != Blocks.air)               structure.setBlock(xx,(int)(yy * yMp),zz,block);
            }
            for (int y=structure.getHighestY(xx,zz); y >= 5; y--) {
              if (structure.getBlock(xx,y,zz) == Blocks.end_stone && structure.getBlock(xx,y + 1,zz).getMaterial() == Material.air) {
                structure.setBlock(xx,y,zz,IslandBiomeBase.getTopBlock(),biome.getTopBlockMeta());
              }
            }
          }
        }
      }
    }
    CaveGenerator caveGen=new CaveGenerator(centerX,25,centerZ,halfSize,20,halfSize);
    caveGen.setup(consistentRand,biome);
    caveGen.generate(structure);
    OreGenerator oreGen=new OreGenerator(8,0,8,size,55,size);
    oreGen.setup(consistentRand,biome);
    oreGen.generate(structure);
    biome.decorateGen(structure,consistentRand,centerX,centerZ);
    structure.setBlock(104,8,104,BlockList.biome_core,biomeData.content.id,true);
    isSetup=true;
  }
  for (int chunkX=0; chunkX < 13; chunkX++) {
    for (int chunkZ=0; chunkZ < 13; chunkZ++) {
      structure.getChunkFromChunkCoords(chunkX,chunkZ).generateInStructure(this,world,bb,8,islandBottomY,8);
    }
  }
  return true;
}

Fixed version (ground truth):
@Override public boolean addComponentParts(World world,Random rand,StructureBoundingBox bb){
  int centerX=sizeX >> 1, centerZ=sizeZ >> 1;
  for (int chunkX=0; chunkX < 13; chunkX++) {
    for (int chunkZ=0; chunkZ < 13; chunkZ++) {
      for (int a=0; a < 16; a++) {
        for (int b=0; b < 16; b++) {
          placeBlockAtCurrentPosition(world,Blocks.emerald_block,0,chunkX * 16 + a,islandBottomY - 4,chunkZ * 16 + b,bb);
        }
      }
    }
  }
  for (int a=0; a < 208; a++) {
    for (int b=0; b < 208; b++) {
      placeBlockAtCurrentPosition(world,Blocks.lapis_block,0,a,islandBottomY - 5,b,bb);
    }
  }
  return true;
}