Program: 57878
Project: 57878
Buggy source:
@Override public void refreshChunk(int x,int z){
  World world=getSpongeWorld();
  Chunk nmsChunk=((net.minecraft.world.World)world).getChunkProvider().provideChunk(x,z);
  if (nmsChunk == null || !nmsChunk.isLoaded()) {
    return;
  }
  try {
    ChunkPos pos=nmsChunk.getChunkCoordIntPair();
    WorldServer w=(WorldServer)nmsChunk.getWorld();
    PlayerChunkMap chunkMap=w.getPlayerChunkMap();
    if (!chunkMap.contains(x,z)) {
      return;
    }
    EntityTracker tracker=w.getEntityTracker();
    HashSet<EntityPlayerMP> players=new HashSet<>();
    for (    EntityPlayer player : w.playerEntities) {
      if (player instanceof EntityPlayerMP) {
        if (chunkMap.isPlayerWatchingChunk((EntityPlayerMP)player,x,z)) {
          players.add((EntityPlayerMP)player);
        }
      }
    }
    if (players.size() == 0) {
      return;
    }
    HashSet<EntityTrackerEntry> entities=new HashSet<>();
    ClassInheritanceMultiMap<Entity>[] entitieSlices=nmsChunk.getEntityLists();
    IntHashMap<EntityTrackerEntry> entries=null;
    for (    Field field : tracker.getClass().getDeclaredFields()) {
      if (field.getType() == IntHashMap.class) {
        field.setAccessible(true);
        entries=(IntHashMap<EntityTrackerEntry>)field.get(tracker);
      }
    }
    for (    ClassInheritanceMultiMap<Entity> slice : entitieSlices) {
      if (slice == null) {
        continue;
      }
      for (      Entity ent : slice) {
        EntityTrackerEntry entry=entries != null ? entries.lookup(ent.getEntityId()) : null;
        if (entry == null) {
          continue;
        }
        entities.add(entry);
        SPacketDestroyEntities packet=new SPacketDestroyEntities(ent.getEntityId());
        for (        EntityPlayerMP player : players) {
          player.connection.sendPacket(packet);
        }
      }
    }
    SPacketChunkData packet=new SPacketChunkData(nmsChunk,65535);
    for (    EntityPlayerMP player : players) {
      player.connection.sendPacket(packet);
    }
    for (    EntityTrackerEntry entry : entities) {
      try {
        TaskManager.IMP.taskLater(new Runnable(){
          @Override public void run(){
            for (            EntityPlayerMP player : players) {
              if (entry.isVisibleTo(player)) {
                entry.removeFromTrackedPlayers(player);
                if (entry.getTrackedEntity() != player) {
                  entry.updatePlayerEntity(player);
                }
              }
            }
          }
        }
,2);
      }
 catch (      Throwable e) {
        e.printStackTrace();
      }
    }
  }
 catch (  Throwable e) {
    e.printStackTrace();
  }
}

Fixed version (ground truth):
@Override public void refreshChunk(int x,int z){
  World world=getSpongeWorld();
  Chunk nmsChunk=((net.minecraft.world.World)world).getChunkProvider().provideChunk(x,z);
  if (nmsChunk == null || !nmsChunk.isLoaded()) {
    return;
  }
  try {
    ChunkPos pos=nmsChunk.getChunkCoordIntPair();
    WorldServer w=(WorldServer)nmsChunk.getWorld();
    PlayerChunkMap chunkMap=w.getPlayerChunkMap();
    if (!chunkMap.contains(x,z)) {
      return;
    }
    EntityTracker tracker=w.getEntityTracker();
    HashSet<EntityPlayerMP> players=new HashSet<>();
    for (    EntityPlayer player : w.playerEntities) {
      if (player instanceof EntityPlayerMP) {
        if (chunkMap.isPlayerWatchingChunk((EntityPlayerMP)player,x,z)) {
          players.add((EntityPlayerMP)player);
        }
      }
    }
    if (players.isEmpty()) {
      return;
    }
    HashSet<EntityTrackerEntry> entities=new HashSet<>();
    ClassInheritanceMultiMap<Entity>[] entitieSlices=nmsChunk.getEntityLists();
    IntHashMap<EntityTrackerEntry> entries=null;
    for (    Field field : tracker.getClass().getDeclaredFields()) {
      if (field.getType() == IntHashMap.class) {
        field.setAccessible(true);
        entries=(IntHashMap<EntityTrackerEntry>)field.get(tracker);
      }
    }
    for (    ClassInheritanceMultiMap<Entity> slice : entitieSlices) {
      if (slice == null) {
        continue;
      }
      for (      Entity ent : slice) {
        EntityTrackerEntry entry=entries != null ? entries.lookup(ent.getEntityId()) : null;
        if (entry == null) {
          continue;
        }
        entities.add(entry);
        SPacketDestroyEntities packet=new SPacketDestroyEntities(ent.getEntityId());
        for (        EntityPlayerMP player : players) {
          player.connection.sendPacket(packet);
        }
      }
    }
    SPacketChunkData packet=new SPacketChunkData(nmsChunk,65535);
    for (    EntityPlayerMP player : players) {
      player.connection.sendPacket(packet);
    }
    for (    EntityTrackerEntry entry : entities) {
      try {
        TaskManager.IMP.taskLater(new Runnable(){
          @Override public void run(){
            for (            EntityPlayerMP player : players) {
              if (entry.isVisibleTo(player)) {
                entry.removeFromTrackedPlayers(player);
                if (entry.getTrackedEntity() != player) {
                  entry.updatePlayerEntity(player);
                }
              }
            }
          }
        }
,2);
      }
 catch (      Throwable e) {
        e.printStackTrace();
      }
    }
  }
 catch (  Throwable e) {
    e.printStackTrace();
  }
}