Strategy tester on "All symbols selected in market watch" - Different result compare to single symbol test result

[Corentin]

HI there,

I have developed a very simple EA trading script (I am newbie) which buy when it receives the first tick of a symbol and sell 20 days after.

When I launch the script on a single symbol with the strategy tester, I got a correct result. But when I launch the strategy tester on "All Symbols selected in the market watch" only the result of the first symbol in the "optimizing results" tab is ok the results of the other tokens are completely random :
- the profit of each token differs from the profit of the single run test
- also, I have the error messages : BASED : 2021.04.10 02:32 - 2021.04.10 23:59  1 minute bars absent within a day while real ticks present ( I thought that when we launch the test with  modelling = every ticks based on real ticks, it only ready the ticks and not the minute bars)

More information :

- the symbols are custom symbols (ticks imported from a CSV).
- Modelling : every ticks based on real ticks

Code extract : 

CTrade            m_Trade;                            
CPositionInfo     m_Position;                      

datetime firstTick = 0;
datetime creationTimestamp = 0;
bool newToken = false;
int investmentCount = 0;

void OnTick()
  {
   MqlTick currentTick;       // To receive last tick data
   SymbolInfoTick(_Symbol,currentTick);

  if (firstTick == 0) {
      firstTick = currentTick.time;
      if (firstTick > StringToTime("2020.11.01")) {
         creationTimestamp = firstTick;
         newToken = true;
      }
   }

    if (newToken) {
         if (positionVolume() == 0 && investmentCount == 0) {
    	    m_Trade.Buy(1/currentTick.ask,my_symbol);
            investmentCount++;
         }
         
         if (positionVolume() > 0) {
            if (currentTick.time > (creationTimestamp+(investmentDuration*24*60*60))) {
               m_Trade.PositionClose(_Symbol);
            }
         }
    }
  return;
}

Did i wrote something wrong ? Your help is much appreciated :).

Thanks !