Program: 25890
Project: 25890
Buggy source:
@SuppressWarnings("String_Node_Str") @Override public int runMoveCheck(Player p,Location to,Location from,double yd,double md,MoveData movedata,boolean up,boolean inwater,boolean onladder,XYZ lg){
  if (p.isFlying()) {
    return 0;
  }
  if (!p.getAllowFlight()) {
    if (to.getBlockY() != from.getBlockY()) {
      if (up && p.isOnGround() && !inwater) {
        if (p.getVelocity().getY() < 0) {
          int id=this.vars.raiseViolationLevel(CheckType.NOFALL,p);
          ViolationTriggeredEvent vte=new ViolationTriggeredEvent(id,CheckType.NOFALL,p);
          Bukkit.getServer().getPluginManager().callEvent(vte);
          if (!vte.isCancelled()) {
            if (id != 0) {
              String message=Setting.nofallmessage;
              message=message.replaceAll("String_Node_Str",ChatColor.YELLOW + "String_Node_Str" + p.getName()+ "String_Node_Str"+ ChatColor.GREEN);
              message=message.replaceAll("String_Node_Str",id + "String_Node_Str");
              Utils.messageAdmins(message);
            }
            return 4;
          }
        }
      }
    }
  }
  if (!up && yd > 0.25 && p.isOnGround()) {
    int id=this.vars.raiseViolationLevel(CheckType.NOFALL,p);
    ViolationTriggeredEvent vte=new ViolationTriggeredEvent(id,CheckType.NOFALL,p);
    Bukkit.getServer().getPluginManager().callEvent(vte);
    if (!vte.isCancelled()) {
      if (id != 0) {
        String message=Setting.nofallmessage;
        message=message.replaceAll("String_Node_Str",ChatColor.YELLOW + "String_Node_Str" + p.getName()+ "String_Node_Str"+ ChatColor.GREEN);
        message=message.replaceAll("String_Node_Str",id + "String_Node_Str");
        Utils.messageAdmins(message);
      }
      return 4;
    }
  }
  return 0;
}

Fixed version (ground truth):
@SuppressWarnings("String_Node_Str") @Override public int runMoveCheck(Player p,Location to,Location from,double yd,double md,MoveData movedata,boolean up,boolean inwater,boolean onladder,XYZ lg){
  if (p.isFlying()) {
    return 0;
  }
  if (!p.getAllowFlight()) {
    if (to.getBlockY() != from.getBlockY()) {
      if (up && p.isOnGround() && !inwater) {
        if (p.getVelocity().getY() < 0) {
          Material m=from.getBlock().getType();
          if (m != Material.CHEST && m != Material.TRAPPED_CHEST) {
            return 0;
          }
          int id=this.vars.raiseViolationLevel(CheckType.NOFALL,p);
          ViolationTriggeredEvent vte=new ViolationTriggeredEvent(id,CheckType.NOFALL,p);
          Bukkit.getServer().getPluginManager().callEvent(vte);
          if (!vte.isCancelled()) {
            if (id != 0) {
              String message=Setting.nofallmessage;
              message=message.replaceAll("String_Node_Str",ChatColor.YELLOW + "String_Node_Str" + p.getName()+ "String_Node_Str"+ ChatColor.GREEN);
              message=message.replaceAll("String_Node_Str",id + "String_Node_Str");
              Utils.messageAdmins(message);
            }
            return 4;
          }
        }
      }
    }
  }
  if (!up && yd > 0.25 && p.isOnGround()) {
    int id=this.vars.raiseViolationLevel(CheckType.NOFALL,p);
    ViolationTriggeredEvent vte=new ViolationTriggeredEvent(id,CheckType.NOFALL,p);
    Bukkit.getServer().getPluginManager().callEvent(vte);
    if (!vte.isCancelled()) {
      if (id != 0) {
        String message=Setting.nofallmessage;
        message=message.replaceAll("String_Node_Str",ChatColor.YELLOW + "String_Node_Str" + p.getName()+ "String_Node_Str"+ ChatColor.GREEN);
        message=message.replaceAll("String_Node_Str",id + "String_Node_Str");
        Utils.messageAdmins(message);
      }
      return 4;
    }
  }
  return 0;
}