MT5 error 10004: Requote

#include <Trade/Trade.mqh>
CTrade trade;

void OpenBuy(const double lots)
  {
   trade.SetDeviationInPoints(0);          // not one point of slippage allowed
   if(!trade.Buy(lots, _Symbol))
      Print("Buy failed: ", trade.ResultRetcode());
  }

#include <Trade/Trade.mqh>
CTrade trade;

void OpenBuy(const double lots)
  {
   trade.SetDeviationInPoints(20);         // accept up to 20 points from the requested price
   for(int attempt = 0; attempt < 3; attempt++)
     {
      if(trade.Buy(lots, _Symbol))           // price 0: CTrade reads a fresh Ask each time
         return;
      const uint code = trade.ResultRetcode();
      if(code != TRADE_RETCODE_REQUOTE && code != TRADE_RETCODE_PRICE_CHANGED)
         break;
     }
   Print("Buy failed: ", trade.ResultRetcode(), " ", trade.ResultComment());
  }