Program: 46571
Project: 46571
Buggy source:
/** 
 * Called by Bukkit, main code block for this class
 */
public void onBlockDamage(BlockDamageEvent event){
  event.setCancelled(true);
  Block block=event.getBlock();
  Player player=event.getPlayer();
  DLPlayerConfig pConfig=plugin.dlUsers.get(player);
  if (plugin.enabled(player) && player.getItemInHand().getTypeId() == pConfig.wandItem) {
    if (plugin.debug) {
      log.info("String_Node_Str" + player.getName() + "String_Node_Str"+ block.getX()+ "String_Node_Str"+ block.getY()+ "String_Node_Str"+ block.getZ());
    }
    if (block.getType() == (pConfig.chestMode ? Material.CHEST : Material.DISPENSER)) {
      String blockTypeStringUCase=(pConfig.chestMode ? "String_Node_Str" : "String_Node_Str");
      if (pConfig.blockAreaMode == false) {
        ContainerBlock targetBlock=(ContainerBlock)event.getBlock().getState();
        if (pConfig.singleClearMode) {
          blockInterface.emptyContainer(targetBlock);
          if (pConfig.clearOnce) {
            pConfig.clearOnce=false;
            pConfig.singleClearMode=false;
          }
          player.sendMessage(ChatColor.DARK_AQUA + blockTypeStringUCase + "String_Node_Str");
          if (plugin.debug)           log.info("String_Node_Str" + blockTypeStringUCase + "String_Node_Str"+ player.getName()+ "String_Node_Str");
        }
        if (pConfig.singleFillMode) {
          blockInterface.fill(targetBlock,pConfig.material,pConfig.damageValue);
          if (pConfig.fillOnce) {
            plugin.dlUsers.get(player).fillOnce=false;
            plugin.dlUsers.get(player).singleFillMode=false;
          }
          player.sendMessage(ChatColor.DARK_AQUA + blockTypeStringUCase + "String_Node_Str"+ pConfig.material);
          if (plugin.debug)           log.info("String_Node_Str" + blockTypeStringUCase + "String_Node_Str"+ player.getName()+ "String_Node_Str"+ pConfig.material+ "String_Node_Str");
        }
        if (!pConfig.singleClearMode && !pConfig.singleFillMode) {
          blockInterface.add(targetBlock,pConfig.material,pConfig.amount,pConfig.damageValue);
          player.sendMessage(ChatColor.DARK_AQUA + blockTypeStringUCase + "String_Node_Str"+ pConfig.amount+ "String_Node_Str"+ pConfig.material);
          if (plugin.debug)           log.info("String_Node_Str" + blockTypeStringUCase + "String_Node_Str"+ player.getName()+ "String_Node_Str"+ pConfig.material+ "String_Node_Str"+ pConfig.amount+ "String_Node_Str");
        }
      }
    }
    if (pConfig.blockAreaMode == true) {
      Block firstBlock=pConfig.areaBlock1;
      Block secondBlock=pConfig.areaBlock2;
      if (firstBlock instanceof Block && secondBlock instanceof Block) {
        if (pConfig.lastAreaBlockSet == 1) {
          pConfig.areaBlock2=block;
          sendBlockSetMsg(2,player,block);
          pConfig.lastAreaBlockSet=2;
          if (plugin.debug) {
            log.info("String_Node_Str" + player.getName() + "String_Node_Str");
          }
        }
 else {
          pConfig.areaBlock1=block;
          sendBlockSetMsg(1,player,block);
          pConfig.lastAreaBlockSet=1;
          if (plugin.debug) {
            log.info("String_Node_Str" + player.getName() + "String_Node_Str");
          }
        }
        return;
      }
      if (firstBlock instanceof Block && !(secondBlock instanceof Block)) {
        pConfig.areaBlock2=block;
        sendBlockSetMsg(2,player,block);
        pConfig.lastAreaBlockSet=2;
        if (plugin.debug) {
          log.info("String_Node_Str" + player.getName() + "String_Node_Str");
        }
        return;
      }
      if (!(firstBlock instanceof Block)) {
        pConfig.areaBlock1=block;
        sendBlockSetMsg(1,player,block);
        pConfig.lastAreaBlockSet=1;
        if (plugin.debug) {
          log.info("String_Node_Str" + player.getName() + "String_Node_Str");
        }
        return;
      }
    }
  }
}

Fixed version (ground truth):
/** 
 * Called by Bukkit, main code block for this class
 */
public void onBlockDamage(BlockDamageEvent event){
  Block block=event.getBlock();
  Player player=event.getPlayer();
  DLPlayerConfig pConfig=plugin.dlUsers.get(player);
  if (plugin.enabled(player) && player.getItemInHand().getTypeId() == pConfig.wandItem) {
    event.setCancelled(true);
    if (plugin.debug) {
      log.info("String_Node_Str" + player.getName() + "String_Node_Str"+ block.getX()+ "String_Node_Str"+ block.getY()+ "String_Node_Str"+ block.getZ());
    }
    if (block.getType() == (pConfig.chestMode ? Material.CHEST : Material.DISPENSER)) {
      String blockTypeStringUCase=(pConfig.chestMode ? "String_Node_Str" : "String_Node_Str");
      if (pConfig.blockAreaMode == false) {
        ContainerBlock targetBlock=(ContainerBlock)event.getBlock().getState();
        if (pConfig.singleClearMode) {
          blockInterface.emptyContainer(targetBlock);
          if (pConfig.clearOnce) {
            pConfig.clearOnce=false;
            pConfig.singleClearMode=false;
          }
          player.sendMessage(ChatColor.DARK_AQUA + blockTypeStringUCase + "String_Node_Str");
          if (plugin.debug)           log.info("String_Node_Str" + blockTypeStringUCase + "String_Node_Str"+ player.getName()+ "String_Node_Str");
        }
        if (pConfig.singleFillMode) {
          blockInterface.fill(targetBlock,pConfig.material,pConfig.damageValue);
          if (pConfig.fillOnce) {
            plugin.dlUsers.get(player).fillOnce=false;
            plugin.dlUsers.get(player).singleFillMode=false;
          }
          player.sendMessage(ChatColor.DARK_AQUA + blockTypeStringUCase + "String_Node_Str"+ pConfig.material);
          if (plugin.debug)           log.info("String_Node_Str" + blockTypeStringUCase + "String_Node_Str"+ player.getName()+ "String_Node_Str"+ pConfig.material+ "String_Node_Str");
        }
        if (!pConfig.singleClearMode && !pConfig.singleFillMode) {
          blockInterface.add(targetBlock,pConfig.material,pConfig.amount,pConfig.damageValue);
          player.sendMessage(ChatColor.DARK_AQUA + blockTypeStringUCase + "String_Node_Str"+ pConfig.amount+ "String_Node_Str"+ pConfig.material);
          if (plugin.debug)           log.info("String_Node_Str" + blockTypeStringUCase + "String_Node_Str"+ player.getName()+ "String_Node_Str"+ pConfig.material+ "String_Node_Str"+ pConfig.amount+ "String_Node_Str");
        }
      }
    }
    if (pConfig.blockAreaMode == true) {
      Block firstBlock=pConfig.areaBlock1;
      Block secondBlock=pConfig.areaBlock2;
      if (firstBlock instanceof Block && secondBlock instanceof Block) {
        if (pConfig.lastAreaBlockSet == 1) {
          pConfig.areaBlock2=block;
          sendBlockSetMsg(2,player,block);
          pConfig.lastAreaBlockSet=2;
          if (plugin.debug) {
            log.info("String_Node_Str" + player.getName() + "String_Node_Str");
          }
        }
 else {
          pConfig.areaBlock1=block;
          sendBlockSetMsg(1,player,block);
          pConfig.lastAreaBlockSet=1;
          if (plugin.debug) {
            log.info("String_Node_Str" + player.getName() + "String_Node_Str");
          }
        }
        return;
      }
      if (firstBlock instanceof Block && !(secondBlock instanceof Block)) {
        pConfig.areaBlock2=block;
        sendBlockSetMsg(2,player,block);
        pConfig.lastAreaBlockSet=2;
        if (plugin.debug) {
          log.info("String_Node_Str" + player.getName() + "String_Node_Str");
        }
        return;
      }
      if (!(firstBlock instanceof Block)) {
        pConfig.areaBlock1=block;
        sendBlockSetMsg(1,player,block);
        pConfig.lastAreaBlockSet=1;
        if (plugin.debug) {
          log.info("String_Node_Str" + player.getName() + "String_Node_Str");
        }
        return;
      }
    }
  }
}