Program: 46541
Project: 46541
Buggy source:
@Override public void onPlayerMove(final PlayerMoveEvent event){
  Location target=event.getTo();
  World world=target.getWorld();
  permissionsPlugin=plugin.getServer().getPluginManager().getPlugin("String_Node_Str");
  final Block block=world.getBlockAt(new Location(world,target.getX(),target.getY() - 1,target.getZ()));
  final Block blockxs=world.getBlockAt(new Location(world,target.getX() - 0.4,target.getY(),target.getZ()));
  final Block blockxp=world.getBlockAt(new Location(world,target.getX() + 0.4,target.getY(),target.getZ()));
  final Block blockzs=world.getBlockAt(new Location(world,target.getX(),target.getY(),target.getZ() - 0.4));
  final Block blockzp=world.getBlockAt(new Location(world,target.getX(),target.getY(),target.getZ() + 0.4));
  dmgDealt=props.damageDealt * 2;
  dmgDelay=props.damageDelay * 20;
  air=new ItemStack(Material.AIR);
  if (block.getType() == Material.NETHERRACK || blockxs.getType() == Material.NETHERRACK || blockxp.getType() == Material.NETHERRACK || blockzs.getType() == Material.NETHERRACK || blockzp.getType() == Material.NETHERRACK) {
    if (IsFirst == 0) {
      if (!event.getPlayer().getInventory().getBoots().equals(air) && props.bootMod.equals("String_Node_Str")) {
        dmgDealt=dmgDealt / 2;
      }
      if (permissionsPlugin != null) {
        if (!(plugin).permissionHandler.has(event.getPlayer(),"String_Node_Str")) {
          IsDmg=1;
          IsFirst=1;
          id=Bukkit.getServer().getScheduler().scheduleAsyncRepeatingTask(plugin,new Runnable(){
            public void run(){
              event.getPlayer().damage(dmgDealt);
            }
          }
,0L,dmgDelay);
        }
      }
 else {
        if (!event.getPlayer().isOp()) {
          IsDmg=1;
          IsFirst=1;
          id=Bukkit.getServer().getScheduler().scheduleAsyncRepeatingTask(plugin,new Runnable(){
            public void run(){
              event.getPlayer().damage(dmgDealt);
            }
          }
,0L,dmgDelay);
        }
      }
    }
  }
 else {
    if (IsDmg == 1) {
      Bukkit.getServer().getScheduler().cancelTask(id);
      IsDmg=0;
      IsFirst=0;
    }
  }
}

Fixed version (ground truth):
@Override public void onPlayerMove(final PlayerMoveEvent event){
  Location target=event.getTo();
  World world=target.getWorld();
  permissionsPlugin=plugin.getServer().getPluginManager().getPlugin("String_Node_Str");
  final Block block=world.getBlockAt(new Location(world,target.getX(),target.getY() - 1,target.getZ()));
  final Block blockxs=world.getBlockAt(new Location(world,target.getX() - 0.4,target.getY(),target.getZ()));
  final Block blockxp=world.getBlockAt(new Location(world,target.getX() + 0.4,target.getY(),target.getZ()));
  final Block blockzs=world.getBlockAt(new Location(world,target.getX(),target.getY(),target.getZ() - 0.4));
  final Block blockzp=world.getBlockAt(new Location(world,target.getX(),target.getY(),target.getZ() + 0.4));
  dmgDealt=props.damageDealt * 2;
  dmgDelay=props.damageDelay * 20;
  air=new ItemStack(Material.AIR);
  if (block.getType() == Material.NETHERRACK || blockxs.getType() == Material.NETHERRACK || blockxp.getType() == Material.NETHERRACK || blockzs.getType() == Material.NETHERRACK || blockzp.getType() == Material.NETHERRACK) {
    if (IsFirst == 0) {
      if (!event.getPlayer().getInventory().getBoots().equals(air) && props.bootMod.equals("String_Node_Str")) {
        dmgDealt=dmgDealt / 2;
      }
      if (permissionsPlugin != null) {
        if (!(plugin).permissionHandler.has(event.getPlayer(),"String_Node_Str")) {
          IsDmg=1;
          IsFirst=1;
          id=Bukkit.getServer().getScheduler().scheduleAsyncRepeatingTask(plugin,new Runnable(){
            public void run(){
              event.getPlayer().damage(dmgDealt);
            }
          }
,0L,dmgDelay);
        }
      }
 else {
        if (!event.getPlayer().isOp()) {
          IsDmg=1;
          IsFirst=1;
          id=Bukkit.getServer().getScheduler().scheduleAsyncRepeatingTask(plugin,new Runnable(){
            public void run(){
              event.getPlayer().damage(dmgDealt);
            }
          }
,0L,dmgDelay);
        }
      }
    }
  }
 else {
    if (IsDmg == 1) {
      Bukkit.getServer().getScheduler().cancelTask(id);
      Bukkit.getServer().getScheduler().cancelAllTasks();
      IsDmg=0;
      IsFirst=0;
    }
  }
}