MetaStrategy-doesn-t-behave-as-expected

Run the following code in 5-minute interval: once with VXX as the default 'Single Symbol', and once as "SPY".

CODE:
using WealthLab.Backtest;
using System;
using WealthLab.Core;
using WealthLab.Data;
using WealthLab.Indicators;
using System.Collections.Generic;


namespace WealthScript3 
{
    public class MyStrategy : UserStrategyBase
    {
      BarHistory barsToUse = null;
        public override void Initialize(BarHistory bars)
        {
         barsToUse = GetHistory(bars, "VXX");
         StartIndex = 1;
        }

        //execute the strategy rules here, this is executed once for each bar in the backtest history
        public override void Execute(BarHistory bars, int bar)
        {
         int barTime = bars.DateTimes[bar].Hour * 100 + bars.DateTimes[bar].Minute;

         Position position = GetPositionsAllSymbols(true).Count > 0 ? GetPositionsAllSymbols(true)[0] : null;
            if (position == null  && bar == StartIndex)
            {
            PlaceTrade(barsToUse, TransactionType.Buy, OrderType.Market);
            }
            else
            {
               if(barTime >= 1555 && position != null && position.IsOpen)
            {
               Transaction transaction = PlaceTrade(position.Bars, TransactionType.Sell, OrderType.Market);
               if(bars.Symbol != "VXX")
               {
                  transaction.Quantity = position.Quantity -1;
               }
                  
            }
            }
        }

        //declare private variables below

    }
}

It should close the position when "VXX" is the bar's symbol, but leave the position open with one share if the symbol is 'SPY'.

Next, create a MetaStrategy and apply the same strategy twice: once with VXX and once with SPY as the symbol to run on. You will notice that for SPY, the entire position remains open instead of just one share.

Expected: MetaStrategy to work as running the strategy standalone.