Program: 25881
Project: 25881
Buggy source:
@SuppressWarnings("String_Node_Str") @Override public int runMoveCheck(Player p,Location to,Location from,double yd,double xs,double zs,MoveData movedata,boolean up,boolean inwater,boolean onladder,XYZ lg){
  if (p.isFlying()) {
    return 0;
  }
  if (!inwater) {
    if (to.getBlockX() != from.getBlockX() || to.getBlockZ() != from.getBlockZ()) {
      int by=to.getBlockY();
      int oy=by;
      while (true) {
        by--;
        if (to.getBlock().getRelative(0,((oy - by) * -1),0).getType().isSolid()) {
          break;
        }
        if (by < 0) {
          break;
        }
      }
      int dis=(oy - by);
      if (dis > 2 && p.isOnGround()) {
        int id=this.vars.raiseViolationLevel(CheckType.FLY,p);
        ViolationTriggeredEvent vte=new ViolationTriggeredEvent(id,CheckType.FLY,p);
        Bukkit.getServer().getPluginManager().callEvent(vte);
        if (!vte.isCancelled()) {
          if (id != 0) {
            String message=Setting.flymes;
            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 1;
        }
      }
 else       if (dis < 1 && !p.isOnGround()) {
        int id=this.vars.raiseViolationLevel(CheckType.IMPOSSIBLE,p);
        ViolationTriggeredEvent vte=new ViolationTriggeredEvent(id,CheckType.IMPOSSIBLE,p);
        Bukkit.getServer().getPluginManager().callEvent(vte);
        if (!vte.isCancelled()) {
          if (id != 0) {
            String message=Setting.impossiblemovemes;
            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 1;
        }
      }
    }
  }
  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;
}

Fixed version (ground truth):
@SuppressWarnings("String_Node_Str") @Override public int runMoveCheck(Player p,Location to,Location from,double yd,double xs,double zs,MoveData movedata,boolean up,boolean inwater,boolean onladder,XYZ lg){
  if (p.isFlying()) {
    return 0;
  }
  if (!inwater && !p.getAllowFlight() && p.isOnGround()) {
    Material m=null;
    if (to.getBlockX() != from.getBlockX() || to.getBlockZ() != from.getBlockZ()) {
      int by=from.getBlockY() + 1;
      int oy=by;
      boolean con=true;
      while (con) {
        by--;
        m=from.getBlock().getRelative(0,((oy - by) * -1) + 1,0).getType();
        if (m.isSolid()) {
          con=false;
          break;
        }
        if (by < 0) {
          con=false;
          break;
        }
      }
      int dis=(oy - by);
      if (dis > 2) {
        int id=this.vars.raiseViolationLevel(CheckType.FLY,p);
        ViolationTriggeredEvent vte=new ViolationTriggeredEvent(id,CheckType.FLY,p);
        Bukkit.getServer().getPluginManager().callEvent(vte);
        if (!vte.isCancelled()) {
          if (id != 0) {
            String message=Setting.flymes;
            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 1;
        }
      }
    }
  }
  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;
}