Crashed in OnStart

Not sure what ive done - bu ti get this message when backtesting a bot i wrote.

12/05/2019 21:01:00.123 | Crashed in OnStart with ArgumentException: Incorrect parameters count. Parameter name: parameterValues

This is the code. I cant See 'parameterValues' anywhere.

using System;
using System.Linq;
using cAlgo.API;
using cAlgo.API.Indicators;
using cAlgo.API.Internals;
using cAlgo.Indicators;

namespace cAlgo.Robots
{
    [Robot(TimeZone = TimeZones.UTC, AccessRights = AccessRights.None)]
    public class Scalper01 : Robot
    {
        [Parameter("Volume", DefaultValue = 1000, MinValue = 1000, Step = 1000)]
        public int _vol { get; set; }

        private VWAP _vwap;
        private ExponentialMovingAverage _emaf;
        private ExponentialMovingAverage _emas;
        private StochasticOscillator _stoch;


        private double _tp;
        private double _sl;

        protected override void OnStart()
        {
            _vwap = Indicators.GetIndicator<VWAP>();
            _emaf = Indicators.ExponentialMovingAverage(MarketSeries.Close, 13);
            _emas = Indicators.ExponentialMovingAverage(MarketSeries.Close, 66);
            _stoch = Indicators.StochasticOscillator(5, 3, 3, MovingAverageType.Exponential);
            _tp = 9.0;
            _sl = 3.0;

        }

        protected override void OnTick()
        {
            double _price = MarketSeries.Close.Count;
            double _emafPrice = _emaf.Result.Count;

            var _longPos = Positions.Find(null, Symbol, TradeType.Buy);
            var _shortPos = Positions.Find(null, Symbol, TradeType.Sell);
            var _vwapup = _vwap.Result.IsRising();
            var _vwapdn = _vwap.Result.IsFalling();
            var _emafres = _emaf.Result.Last(0);
            var _emasres = _emas.Result.Last(0);
            var _stochup = _stoch.PercentD.HasCrossedAbove(21, 3);
            var _stochdn = _stoch.PercentD.HasCrossedBelow(79, 3);

            if (_vwapup && _stochup == true)
            {
                if (_emafres > _emasres && _stochup == true)
                {
                    if (_price == _emafPrice)
                        if (_longPos != null)
                            ExecuteMarketOrder(TradeType.Buy, Symbol, _vol, null, _sl, _tp);
                }
            }

            if (_vwapdn == true)
            {
                if (_emafres < _emasres && _stochdn == true)
                {
                    if (_price == _emafPrice)

                        if (_shortPos != null)
                            ExecuteMarketOrder(TradeType.Sell, Symbol, _vol, null, _sl, _tp);
                }
            }


        }

        protected override void OnStop()
        {
            // Put your deinitialization logic here
        }
    }
}