Charts in tableView : Not working well

Question

I am customising ios charts as per my need and showing them in a tabel view. For the first time they look different and after scrolling and reloading they look better.

I have taken a view inside a cell and adding chart as a subview.

Here is my code :

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {

let heartRateCell = tableView.dequeueReusableCell(withIdentifier: "HeartRateCell", for: indexPath) as! HeartRateCell
            heartRateCell.backgroundColor = UIColor.clear
            print(stackedChartData)
            while let subview = heartRateCell.heartRateChartView.subviews.last {
                subview.removeFromSuperview()
            }
            let chartview = CustomLineChart(frame : heartRateCell.heartRateChartView.frame)
            print(heartRateCell.heartRateChartView.frame)
            //chartview.frame = heartRateCell.heartRateChartView.frame

            chartview.setupLineChart(data: heartRateData)
            heartRateCell.heartRateChartView.addSubview(chartview)
            heartRateCell.heartRateChartView.bringSubview(toFront: chartview)
            heartRateCell.heartRateChartView.layoutIfNeeded()

            return heartRateCell
}

Here are images before and after scrolling (or reloading ).

Any Idea why it is behaving like this ? thanks.