Program: 177313
Project: 177313
Buggy source:
public void preSnapshotRun(){
  entityManager.preSnapshotRun();
  SpoutWorld world=this.getWorld();
  boolean worldRenderQueueEnabled=world.isRenderQueueEnabled();
  boolean firstRenderQueueTick=(!renderQueueEnabled) && worldRenderQueueEnabled;
  renderQueueEnabled=worldRenderQueueEnabled;
  if (firstRenderQueueTick) {
    for (int dx=0; dx < CHUNKS.SIZE; dx++) {
      for (int dy=0; dy < CHUNKS.SIZE; dy++) {
        for (int dz=0; dz < CHUNKS.SIZE; dz++) {
          SpoutChunk chunk=chunks[dx][dy][dz].get();
          if (chunk != null) {
            addUpdateToRenderQueue(chunk);
          }
        }
      }
    }
  }
  SpoutChunk spoutChunk;
  while ((spoutChunk=dirtyChunks.poll()) != null) {
    spoutChunk.setNotDirtyQueued();
    if (!spoutChunk.isLoaded()) {
      continue;
    }
    if ((!firstRenderQueueTick) && renderQueueEnabled && spoutChunk.isRenderDirty()) {
      spoutChunk.setRenderDirty(false);
      addUpdateToRenderQueue(spoutChunk);
    }
    if (spoutChunk.isPopulated() && spoutChunk.isDirty()) {
      for (      Player entity : spoutChunk.getObservingPlayers()) {
        syncChunkToPlayer(spoutChunk,entity);
      }
      processChunkUpdatedEvent(spoutChunk);
      spoutChunk.resetDirtyArrays();
      spoutChunk.setLightDirty(false);
    }
  }
  SpoutChunkSnapshotFuture snapshotFuture;
  while ((snapshotFuture=snapshotQueue.poll()) != null) {
    snapshotFuture.run();
  }
  renderSnapshotCache.clear();
  for (int dx=0; dx < CHUNKS.SIZE; dx++) {
    for (int dy=0; dy < CHUNKS.SIZE; dy++) {
      for (int dz=0; dz < CHUNKS.SIZE; dz++) {
        SpoutChunk chunk=chunks[dx][dy][dz].get();
        if (chunk != null) {
          chunk.updateExpiredObservers();
        }
      }
    }
  }
  entityManager.syncEntities();
}

Fixed version (ground truth):
public void preSnapshotRun(){
  entityManager.preSnapshotRun();
  SpoutWorld world=this.getWorld();
  boolean worldRenderQueueEnabled=world.isRenderQueueEnabled();
  boolean firstRenderQueueTick=(!renderQueueEnabled) && worldRenderQueueEnabled;
  renderQueueEnabled=worldRenderQueueEnabled;
  if (firstRenderQueueTick) {
    for (int dx=0; dx < CHUNKS.SIZE; dx++) {
      for (int dy=0; dy < CHUNKS.SIZE; dy++) {
        for (int dz=0; dz < CHUNKS.SIZE; dz++) {
          SpoutChunk chunk=chunks[dx][dy][dz].get();
          if (chunk != null) {
            addUpdateToRenderQueue(chunk);
          }
        }
      }
    }
  }
  SpoutChunk spoutChunk;
  while ((spoutChunk=dirtyChunks.poll()) != null) {
    spoutChunk.setNotDirtyQueued();
    if (!spoutChunk.isLoaded()) {
      continue;
    }
    if ((!firstRenderQueueTick) && renderQueueEnabled && spoutChunk.isRenderDirty()) {
      addUpdateToRenderQueue(spoutChunk);
    }
    if (spoutChunk.isPopulated() && spoutChunk.isDirty()) {
      for (      Player entity : spoutChunk.getObservingPlayers()) {
        syncChunkToPlayer(spoutChunk,entity);
      }
      processChunkUpdatedEvent(spoutChunk);
      spoutChunk.resetDirtyArrays();
      spoutChunk.setLightDirty(false);
    }
  }
  SpoutChunkSnapshotFuture snapshotFuture;
  while ((snapshotFuture=snapshotQueue.poll()) != null) {
    snapshotFuture.run();
  }
  renderSnapshotCache.clear();
  for (int dx=0; dx < CHUNKS.SIZE; dx++) {
    for (int dy=0; dy < CHUNKS.SIZE; dy++) {
      for (int dz=0; dz < CHUNKS.SIZE; dz++) {
        SpoutChunk chunk=chunks[dx][dy][dz].get();
        if (chunk != null) {
          chunk.updateExpiredObservers();
        }
      }
    }
  }
  entityManager.syncEntities();
}