Program: 44724
Project: 44724
Buggy source:
@Override public void onPlayerInteract(PlayerInteractEvent event){
  if (event.isCancelled() || event.getAction() != Action.RIGHT_CLICK_BLOCK)   return;
  Block block=event.getClickedBlock();
  if (block.getType() != Material.WALL_SIGN && block.getType() != Material.SIGN_POST && block.getType() != Material.CHEST)   return;
  Sign sign;
  if (block.getType() == Material.CHEST) {
    sign=SupplySign.getAttachedSign(block);
    if (sign == null)     return;
  }
 else   sign=new CraftSign(block);
  try {
    if (sign.getLine(0).equals("String_Node_Str")) {
      event.setCancelled(true);
      ArrayList<String> itemList=new ArrayList<String>();
      if (sign.getLine(1).trim().contains("String_Node_Str")) {
        String[] split=sign.getLine(1).trim().split("String_Node_Str");
        if (SupplySign.isAuthorized(event.getPlayer(),"String_Node_Str") || SupplySign.isAuthorized(event.getPlayer(),"String_Node_Str" + split[1]))         itemList=SupplySign.getKit(split[1]);
 else         if (SupplySign.getConfigShowErrorsInClient()) {
          event.getPlayer().sendMessage("String_Node_Str");
          return;
        }
      }
 else {
        if (SupplySign.isAuthorized(event.getPlayer(),"String_Node_Str")) {
          if (!sign.getLine(1).trim().equalsIgnoreCase("String_Node_Str"))           itemList.add(sign.getLine(1).trim());
          if (!sign.getLine(2).trim().equalsIgnoreCase("String_Node_Str"))           itemList.add(sign.getLine(2).trim());
          if (!sign.getLine(3).trim().equalsIgnoreCase("String_Node_Str"))           itemList.add(sign.getLine(3).trim());
        }
 else         if (SupplySign.getConfigShowErrorsInClient()) {
          event.getPlayer().sendMessage("String_Node_Str");
          return;
        }
      }
      if (itemList.size() > 0)       SupplySign.showInventory(event.getPlayer(),itemList);
      return;
    }
  }
 catch (  Throwable ex) {
    if (SupplySign.getConfigShowErrorsInClient())     event.getPlayer().sendMessage("String_Node_Str" + ex.getMessage());
  }
}

Fixed version (ground truth):
@Override public void onPlayerInteract(PlayerInteractEvent event){
  if (event.isCancelled() || event.getAction() != Action.RIGHT_CLICK_BLOCK)   return;
  Block block=event.getClickedBlock();
  if (block.getType() != Material.WALL_SIGN && block.getType() != Material.SIGN_POST && block.getType() != Material.CHEST)   return;
  Sign sign;
  if (block.getType() == Material.CHEST) {
    sign=SupplySign.getAttachedSign(block);
    if (sign == null)     return;
  }
 else   sign=new CraftSign(block);
  try {
    if (sign.getLine(0).equals("String_Node_Str")) {
      event.setCancelled(true);
      ArrayList<Object> itemList=new ArrayList<Object>();
      if (sign.getLine(1).trim().contains("String_Node_Str")) {
        String[] split=sign.getLine(1).trim().split("String_Node_Str");
        if (SupplySign.isAuthorized(event.getPlayer(),"String_Node_Str") || SupplySign.isAuthorized(event.getPlayer(),"String_Node_Str" + split[1]))         itemList=SupplySign.getKit(split[1]);
 else         if (SupplySign.getConfigShowErrorsInClient())         event.getPlayer().sendMessage("String_Node_Str");
      }
 else {
        if (SupplySign.isAuthorized(event.getPlayer(),"String_Node_Str")) {
          if (!sign.getLine(1).trim().equalsIgnoreCase("String_Node_Str"))           itemList.add(sign.getLine(1).trim());
          if (!sign.getLine(2).trim().equalsIgnoreCase("String_Node_Str"))           itemList.add(sign.getLine(2).trim());
          if (!sign.getLine(3).trim().equalsIgnoreCase("String_Node_Str"))           itemList.add(sign.getLine(3).trim());
        }
 else         if (SupplySign.getConfigShowErrorsInClient())         event.getPlayer().sendMessage("String_Node_Str");
      }
      if (itemList.size() > 0)       SupplySign.showInventory(event.getPlayer(),itemList);
      return;
    }
  }
 catch (  Throwable ex) {
    if (SupplySign.getConfigShowErrorsInClient())     event.getPlayer().sendMessage("String_Node_Str" + ex.getMessage());
  }
}