Fail to setup majorDelta in SwiftUI

Hello,
I followed the example swiftui-helper-functions to use SciChart in SwiftUI.It works fine.
But when I try to setup majorDelta according to the max data of data series which is from view model, the chart is hang up.
And the preview of Xcode show this error “PreviewUpdateTimedOutError: Updating took more than 5 seconds”.

Here is part of my code , is there something wrong?

private var yAxis: ISCIAxis {
    let yAxis = SCINumericAxis()
    yAxis.autoRange = .always
    yAxis.growBy = SCIDoubleRange(min: 0, max: 0.1)
    yAxis.axisAlignment = .left
    yAxis.visibleRange = SCIDoubleRange(min: 0, max: viewModel.powerChartModel.powerDataSeries.yMax.toDouble() + PowerView.addVisibleRangeValue)
    yAxis.drawMajorBands = false
    yAxis.drawMajorGridLines = false
    yAxis.drawMinorGridLines = false
    yAxis.drawMinorTicks = false
    yAxis.autoTicks = false
    yAxis.majorDelta = NSNumber(value: round(viewModel.powerChartModel.powerDataSeries.yMax.toDouble() + PowerView.addVisibleRangeValue) * 0.2)
    yAxis.minorDelta = NSNumber(value: 1.0)

    return yAxis
}