How to prevent repainting with this code

Hi everyone, I'm trying to transpose a tradingview indicator in cTrader 

so far that's how I got

using System;
using cAlgo.API;
using cAlgo.API.Indicators;

namespace cAlgo.Indicators
{
    [Indicator(IsOverlay = true, TimeZone = TimeZones.UTC, AccessRights = AccessRights.None)]
    public class KalmanFilterLoxx : Indicator
    {
        [Parameter("Sharpness", DefaultValue = 1.0)]
        public double Sharpness { get; set; }

        [Parameter("K", DefaultValue = 1.0)]
        public double K { get; set; }

        [Output("KF [Loxx]", Color = Colors.Lime)]
        public IndicatorDataSeries kfilt { get; set; }

        private double velocity;
        

        protected override void Initialize()
        {
            velocity = 0.0;
        }

        public override void Calculate(int index)
        {
            var src = (MarketSeries.Close[index] + MarketSeries.Open[index] + MarketSeries.Low[index] + MarketSeries.High[index]) / 4;
            Print("src is " + src);
            Print("prev value " + double.IsNaN(kfilt.LastValue) );
            var prevKfilt = (double.IsNaN(kfilt.LastValue) ? 0 : kfilt.LastValue)  ;
            Print("prevk is " + prevKfilt);
            var distance = src - (prevKfilt == 0 ? src : prevKfilt);
            Print("Distance is " + distance);
            var error = (prevKfilt == 0 ? src : prevKfilt) + distance * Math.Sqrt(Sharpness * K / 100);
            Print("Error is " + error);
            velocity += distance * K / 100;
            Print("Velocity is "+velocity);
            kfilt[index] = error + velocity;

            
        }
    }
}

it works fine when launched but seconds later the last value keeps repainting into oblivion, how to prevent that ?

Original pinescript : 

indicator('Kalman Filter [Loxx]', overlay = true, shorttitle="KF [Loxx]", timeframe="", timeframe_gaps=true)


src = input(ohlc4)
Sharpness = input.float(1.0)
K = input.float(1.0)


greencolor =  color.lime
redcolor =  color.red

velocity = 0.0
kfilt = 0.0

Distance = src - nz(kfilt[1], src)
Error = nz(kfilt[1], src) + Distance * math.sqrt(Sharpness*K/ 100)
velocity := nz(velocity[1], 0) + Distance*K / 100
kfilt := Error + velocity

plot(kfilt, color=velocity > 0 ? greencolor : redcolor, linewidth = 2)