Trailing stop only works with OrderSelect Error

Hello this is my first post. I've been passively reading these forums for 3 month now.... :) But this problem I just can't fix alone and it drives me insane ... ^^

My Expert Advisor should set Trailingstops according to calculated Fibonachi levels. However it seems that the trailing stop is only working, when the OrderSelect after "if(Ticket>0){" produces an error. I find that very confusing, because when the OrderSelect is working the conditions for setting Trailingstops are just ignored or whatever and without this OrderSelect the trailing stop isn't working either.... And second, the trailing stops for the sell orders never work.

I would be happy if some expert is looking into this and can give me any advice... :)

Here is the code, first the included OrderInitiation file and after that the main logic from my EA:

// ...zeroize variables... //
void OneOrderInit( int magic )
{
    int _GetLastError, _OrdersTotal = OrdersTotal()
// ...zeroize variables again... // 

    for ( int z = _OrdersTotal - 1; z >= 0; z -- )
    {
        if ( !OrderSelect( z, SELECT_BY_POS) )
        {
          _GetLastError = GetLastError();
          Print("OrderSelect( ", z, ", SELECT_BY_POS ) - Error #", 
                _GetLastError );
          continue;
        }
        if(OrderMagicNumber() == magic && OrderSymbol() == Symbol())
        {
          _Ticket    = OrderTicket();
          _Type      = OrderType();
          _Lots      = NormalizeDouble( OrderLots(), 1 );
          _OpenPrice = NormalizeDouble( OrderOpenPrice(), Digits);
          _StopLoss = NormalizeDouble( OrderStopLoss(), Digits);
          _TakeProfit = NormalizeDouble( OrderTakeProfit(), Digits);
          _OpenTime   = OrderOpenTime();
          _Profit     = NormalizeDouble( OrderProfit(), 2 );
          _Swap       = NormalizeDouble( OrderSwap(), 2 );
          _Commission = NormalizeDouble( OrderCommission(), 2 );
          _Comment    = OrderComment();
          _Expiration = OrderExpiration();
          return;
        }
    }
}

#include <OneOrderControl.mqh>

extern int slippage = 4;
extern double Lots = 2;
///////////////////////
int ThisBarTrade =  0;
int  magicNumber = 1122;
//+----------------------------------------------------------------------+
extern double SL_S=27;
extern double TP_S=33;
extern double SL_B=27;
extern double TP_B=33;
extern double StopLevel=25;
double newSL_S, newSL_B;
//+----------------------------------------------------------------------+
void StopLevelFiboSell()
  {
  -->sets newSL_S based on FiboLevels
  }
  
void StopLevelFiboBuy()
  {
  -->same
  }
//+------------------------------------------------------------------+
  void Op_Buy_Ch()
  {
   if(!OrderSend(NULL,OP_BUY,Lots,Ask,slippage,Bid-SL_B*Point,Ask+TP_B*Point," ",magicNumber,0,Blue))
     {Print("  SELL order opening error  # ",GetLastError());}
  }
//+------------------------------------------------------------------+
  void Op_Sell_Ch()
  {
   if(!OrderSend(NULL,OP_SELL,Lots,Bid,slippage,Ask+SL_S*Point,Bid-TP_S*Point," ",magicNumber,0,Red))
     {Print("  SELL order opening error  # ",GetLastError());
  }
  }
//+------------------------------------------------------------------+
void Modyf_S_lot()
  {
   if(!OrderModify(_Ticket,_OpenPrice,newSL_S,
      _TakeProfit,0,Aqua))
     {Print(" Modif.ord. Sell# ",_Ticket," Error # ",GetLastError());}return;
  }
// ----------------------------------------------------------------------+
void Modyf_B_lot()
  {
   if(!OrderModify(_Ticket,_OpenPrice,newSL_B,
      _TakeProfit,0,Aqua))
     {Print(" Modif.ord. Buy# ",_Ticket,"Error # ",GetLastError());}return;
  }
//+----------------------------------------------------------------------+
void OnTick()
  {
  int _GetLastError = 0;

  OneOrderInit(magicNumber);

   if (Bars!=ThisBarTrade)
   {
   ThisBarTrade = Bars;                                           //ensure only one trade opportunity per bar
     if (_Ticket>0)                                               //if order is open 
     {
        if(!OrderSelect(1,SELECT_BY_POS,MODE_TRADES))             // << trailing stop only works, when Error
        {Print("Order selection error = ",GetLastError());

        if(_Type == OP_BUY)
        {
                  // ----------------------------------------------------------------------+
                  if((High[1]-_OpenPrice)>=SL_B*Point && _Lots==Lots)Close_B_lot();
                  // ----------------------------------------------------------------------+
                  if((High[1]-_OpenPrice)/Point>=100 && _StopLoss<_OpenPrice)
                    {
                     Print("StopLoss shift #1");
                     if(!OrderModify(_Ticket,_OpenPrice,_OpenPrice+2*Point,
                        _TakeProfit,0,Aqua))
                       {Print(" at Modif.ord. 1 buy# ",_Ticket," Error # ",GetLastError());}return;
                    }
                  // ----------------------------------------------------------------------+
                                        --> next shift, etc
                  //+----------------------------------------------------------------------+
        }
        if(_Type == OP_SELL)
        {
                if((_OpenPrice-Low[1])>=SL_S*Point && OrderLots()==Lots)Close_S_lot();
                  // ----------------------------------------------------------------------+
                  if((_OpenPrice-Low[1])/Point>=100 && OrderLots()==Lots && _StopLoss>_OpenPrice)
                    {
                     if(!OrderModify(_Ticket,_OpenPrice,_OpenPrice-2*Point,_TakeProfit,0,Aqua))
                       {Print(" at Modif.ord. 1 sell# ",_Ticket," Error # ",GetLastError());}return;
                    }
                  // -----------------------------------------------------------------------+
                                            --> next shift etc. 
                  //+----------------------------------------------------------------------+
        }     
    } else 
      {
         if(condition for entry) 
         {
               [...]
         Op_Buy_Ch();
               [...]
         Op_Sell_Ch();
         }
      } return;
   } return;
  }