Program: 34056
Project: 34056
Buggy source:
/** 
 * Teleport to a safe spot on an island
 * @param plugin
 * @param player
 * @param islandLoc
 */
public SafeSpotTeleport(final ASkyBlock plugin,final Player player,final Location islandLoc){
  Island island=plugin.getGrid().getIslandAt(islandLoc);
  if (island != null) {
    World world=islandLoc.getWorld();
    List<ChunkSnapshot> chunkSnapshot=new ArrayList<ChunkSnapshot>();
    chunkSnapshot.add(island.getCenter().toVector().toLocation(world).getChunk().getChunkSnapshot());
    for (int x=islandLoc.getChunk().getX() - 1; x <= islandLoc.getChunk().getX() + 1; x++) {
      for (int z=islandLoc.getChunk().getZ() - 1; z <= islandLoc.getChunk().getZ() + 1; z++) {
        if (x != islandLoc.getChunk().getX() || z != islandLoc.getChunk().getZ()) {
          chunkSnapshot.add(world.getChunkAt(x,z).getChunkSnapshot());
        }
      }
    }
    for (int x=island.getMinProtectedX() / 16; x <= (island.getMinProtectedX() + island.getProtectionSize() - 1) / 16; x++) {
      for (int z=island.getMinProtectedZ() / 16; z <= (island.getMinProtectedZ() + island.getProtectionSize() - 1) / 16; z++) {
        chunkSnapshot.add(world.getChunkAt(x,z).getChunkSnapshot());
      }
    }
    final List<ChunkSnapshot> finalChunk=chunkSnapshot;
    int maxHeight=world.getMaxHeight();
    if (world.getEnvironment().equals(Environment.NETHER)) {
      maxHeight-=20;
    }
    final int worldHeight=maxHeight;
    plugin.getServer().getScheduler().runTaskAsynchronously(plugin,new Runnable(){
      @Override public void run(){
        int x=0;
        int y=0;
        int z=0;
        ChunkSnapshot currentChunk=null;
        boolean safeSpotFound=false;
        search:         for (        ChunkSnapshot chunk : finalChunk) {
          currentChunk=chunk;
          for (x=0; x < 16; x++) {
            for (z=0; z < 16; z++) {
              for (y=0; y <= Math.min(chunk.getHighestBlockYAt(x,z),worldHeight); y++) {
                if (checkBlock(chunk,x,y,z)) {
                  safeSpotFound=true;
                  break search;
                }
              }
            }
          }
        }
        if (currentChunk != null && safeSpotFound) {
          final Vector spot=new Vector((16 * currentChunk.getX()) + x + 0.5D,y,(16 * currentChunk.getZ()) + z + 0.5D);
          plugin.getServer().getScheduler().runTask(plugin,new Runnable(){
            @Override public void run(){
              Location destination=spot.toLocation(islandLoc.getWorld());
              player.teleport(destination);
              if (setHome) {
                plugin.getPlayers().setHomeLocation(player.getUniqueId(),destination,homeNumber);
              }
            }
          }
);
        }
 else {
          plugin.getServer().getScheduler().runTask(plugin,new Runnable(){
            @Override public void run(){
              player.sendMessage(ChatColor.RED + plugin.myLocale(player.getUniqueId()).warpserrorNotSafe);
              if (!failureMessage.isEmpty()) {
                player.sendMessage(failureMessage);
              }
            }
          }
);
        }
      }
      @SuppressWarnings("String_Node_Str") private boolean checkBlock(      ChunkSnapshot chunk,      int x,      int y,      int z){
        int type=chunk.getBlockTypeId(x,y,z);
        if (type != 0) {
          int space1=chunk.getBlockTypeId(x,y + 1,z);
          int space2=chunk.getBlockTypeId(x,y + 2,z);
          if (space1 == 0 && space2 == 0) {
            Material mat=Material.getMaterial(type);
            if (!mat.toString().contains("String_Node_Str") && !mat.toString().contains("String_Node_Str") && !mat.toString().contains("String_Node_Str")&& !mat.toString().contains("String_Node_Str")) {
switch (mat) {
case ANVIL:
case BARRIER:
case BOAT:
case CACTUS:
case DOUBLE_PLANT:
case ENDER_PORTAL:
case FIRE:
case FLOWER_POT:
case LADDER:
case LAVA:
case LEVER:
case LONG_GRASS:
case PISTON_EXTENSION:
case PISTON_MOVING_PIECE:
case PORTAL:
case SIGN_POST:
case SKULL:
case STANDING_BANNER:
case STATIONARY_LAVA:
case STATIONARY_WATER:
case STONE_BUTTON:
case TORCH:
case TRIPWIRE:
case WATER:
case WEB:
case WOOD_BUTTON:
                break;
default :
              return true;
          }
        }
      }
    }
    return false;
  }
}
);
}
}

Fixed version (ground truth):
/** 
 * Teleport to a safe spot on an island
 * @param plugin
 * @param player
 * @param islandLoc
 */
public SafeSpotTeleport(final ASkyBlock plugin,final Player player,final Location islandLoc){
  Island island=plugin.getGrid().getIslandAt(islandLoc);
  if (island != null) {
    World world=islandLoc.getWorld();
    List<ChunkSnapshot> chunkSnapshot=new ArrayList<ChunkSnapshot>();
    chunkSnapshot.add(island.getCenter().toVector().toLocation(world).getChunk().getChunkSnapshot());
    for (int x=islandLoc.getChunk().getX() - 1; x <= islandLoc.getChunk().getX() + 1; x++) {
      for (int z=islandLoc.getChunk().getZ() - 1; z <= islandLoc.getChunk().getZ() + 1; z++) {
        if (x != islandLoc.getChunk().getX() || z != islandLoc.getChunk().getZ()) {
          chunkSnapshot.add(world.getChunkAt(x,z).getChunkSnapshot());
        }
      }
    }
    for (int x=island.getMinProtectedX() / 16; x <= (island.getMinProtectedX() + island.getProtectionSize() - 1) / 16; x++) {
      for (int z=island.getMinProtectedZ() / 16; z <= (island.getMinProtectedZ() + island.getProtectionSize() - 1) / 16; z++) {
        chunkSnapshot.add(world.getChunkAt(x,z).getChunkSnapshot());
      }
    }
    final List<ChunkSnapshot> finalChunk=chunkSnapshot;
    int maxHeight=world.getMaxHeight();
    if (world.getEnvironment().equals(Environment.NETHER)) {
      maxHeight-=20;
    }
    final int worldHeight=maxHeight;
    plugin.getServer().getScheduler().runTaskAsynchronously(plugin,new Runnable(){
      @Override public void run(){
        int x=0;
        int y=0;
        int z=0;
        ChunkSnapshot currentChunk=null;
        boolean safeSpotFound=false;
        search:         for (        ChunkSnapshot chunk : finalChunk) {
          currentChunk=chunk;
          for (x=0; x < 16; x++) {
            for (z=0; z < 16; z++) {
              for (y=0; y <= Math.min(chunk.getHighestBlockYAt(x,z),worldHeight); y++) {
                if (checkBlock(chunk,x,y,z)) {
                  safeSpotFound=true;
                  break search;
                }
              }
            }
          }
        }
        if (currentChunk != null && safeSpotFound) {
          final Vector spot=new Vector((16 * currentChunk.getX()) + x + 0.5D,y,(16 * currentChunk.getZ()) + z + 0.5D);
          plugin.getServer().getScheduler().runTask(plugin,new Runnable(){
            @Override public void run(){
              Location destination=spot.toLocation(islandLoc.getWorld());
              plugin.getLogger().info("String_Node_Str" + destination);
              player.teleport(destination);
              if (setHome) {
                plugin.getPlayers().setHomeLocation(player.getUniqueId(),destination,homeNumber);
              }
            }
          }
);
        }
 else {
          plugin.getServer().getScheduler().runTask(plugin,new Runnable(){
            @Override public void run(){
              player.sendMessage(ChatColor.RED + plugin.myLocale(player.getUniqueId()).warpserrorNotSafe);
              if (!failureMessage.isEmpty()) {
                player.sendMessage(failureMessage);
              }
            }
          }
);
        }
      }
      @SuppressWarnings("String_Node_Str") private boolean checkBlock(      ChunkSnapshot chunk,      int x,      int y,      int z){
        int type=chunk.getBlockTypeId(x,y,z);
        if (type != 0) {
          int space1=chunk.getBlockTypeId(x,y + 1,z);
          int space2=chunk.getBlockTypeId(x,y + 2,z);
          if (space1 == 0 && space2 == 0) {
            Material mat=Material.getMaterial(type);
            if (!mat.toString().contains("String_Node_Str") && !mat.toString().contains("String_Node_Str") && !mat.toString().contains("String_Node_Str")&& !mat.toString().contains("String_Node_Str")) {
switch (mat) {
case ANVIL:
case BARRIER:
case BOAT:
case CACTUS:
case DOUBLE_PLANT:
case ENDER_PORTAL:
case FIRE:
case FLOWER_POT:
case LADDER:
case LAVA:
case LEVER:
case LONG_GRASS:
case PISTON_EXTENSION:
case PISTON_MOVING_PIECE:
case PORTAL:
case SIGN_POST:
case SKULL:
case STANDING_BANNER:
case STATIONARY_LAVA:
case STATIONARY_WATER:
case STONE_BUTTON:
case TORCH:
case TRIPWIRE:
case WATER:
case WEB:
case WOOD_BUTTON:
                break;
default :
              return true;
          }
        }
      }
    }
    return false;
  }
}
);
}
}