ios – SwiftUI ScrollView scrollPosition not updating on autoscroll

The following code fails to update scrollPosition in SwiftUI ScrollView when the user auto-scrolls, i.e. swipes the finger to scroll and picks up the finger immediately. While the scroll view continues scrolling till it decelerates and stops as the finger has been lifted, the scrollPosition is not seen updated in this time. I have not been able to figure out why it is happening.

import SwiftUI
import UIKit

struct ScrubberConfig2 {
    var count:Int
    var majorTickInterval:Int
    var spacing:CGFloat
    let labelFormatter: ((Int) -> String)?
    
    init(count: Int, majorTickInterval: Int, spacing: CGFloat, labelFormatter: ((Int) -> String)? = nil) {
        self.count = count
        self.majorTickInterval = majorTickInterval
        self.spacing = spacing
        self.labelFormatter = labelFormatter
    }
}

struct VerticalScrubber2: View {
    var config: ScrubberConfig2
    @Binding var value: Int
    
    let tickHeight: CGFloat = 5 // 👈 added
    
    @State private var isUserInteracting: Bool = false // New state to track user interaction
    
    @State private var isScrollPositionSet = false // 👈 added
    @State private var scrollPosition:Int?
    
    var body: some View {
        GeometryReader { geometry in
            let verticalPadding = (geometry.size.height - tickHeight) / 2
            
            ZStack(alignment: .trailing) {
                ScrollView(.vertical, showsIndicators: false) {
                    VStack(spacing: config.spacing) {
                        ForEach(0...config.count, id: \.self) { index in
                            horizontalTickMark(for: index)
                                .frame(height: tickHeight)
                                .id(index)
                        }
                    }
                    .frame(width: 80)
                    .scrollTargetLayout()
                }
                .defaultScrollAnchor(.center)
                .scrollTargetBehavior(.viewAligned)
                .scrollPosition(id: $scrollPosition, anchor: .center)
                .contentMargins(.vertical, verticalPadding)
        
                Capsule()
                    .frame(width: 32, height: 3)
                    .foregroundColor(.accentColor)
                    .shadow(color: .accentColor.opacity(0.3), radius: 3, x: 0, y: 1)
            }
            .frame(width: 100)
            .onAppear { 
                scrollPosition = value
            }
            .onChange(of: value, { oldValue, newValue in
                if scrollPosition != newValue, !isUserInteracting {
                    print("📥 Value changed: \(oldValue) → \(newValue)")
                    scrollPosition = newValue
                }
            })
            .onChange(of: scrollPosition, initial: true, { oldValue, newValue in
                if let newValue = newValue, value != newValue, isUserInteracting {
                    print("👆 ScrollPosition changed: \(oldValue ?? -1) → \(newValue)")
                    value = newValue
                }
            })
            .onScrollPhaseChange { oldPhase, newPhase in
                if newPhase == .interacting {
                    isUserInteracting = true
                } else {
                    isUserInteracting = false
                }
            }
        }
    }
    
    private func horizontalTickMark(for index: Int) -> some View {
           let isMajorTick = index % config.majorTickInterval == 0
           
           return HStack(spacing: 8) {
               Rectangle()
                   .fill(isMajorTick ? Color.accentColor : Color.gray.opacity(0.5))
                   .frame(width: isMajorTick ? 24 : 12, height: isMajorTick ? 2 : 1)
               
               if isMajorTick {
                   Text(labelText(for: index))
                       .font(.system(size: 12, weight: .medium))
                       .foregroundColor(.primary)
                       .fixedSize()
               }
           }
           .frame(maxWidth: .infinity, alignment: .trailing)
           .padding(.trailing, 8)
       }
       
       private func labelText(for index: Int) -> String {
           if let formatter = config.labelFormatter {
               return formatter(index)
           } else {
               // Default: show index / steps * 5
               let tickValue = index
               return "\(tickValue)"
           }
       }
}

struct VerticalScrubberPreview2: View {
    @State private var value: Int = 0
    private let config = ScrubberConfig2(count: 100, majorTickInterval: 5, spacing: 5)
    
    var body: some View {
        Text("Vertical Scrubber (0–100 in steps of 5)")
            .font(.title2)
            .padding()
        
        HStack(spacing: 30) {
            VerticalScrubber2(config: config, value: $value)
                .frame(width:120, height: 300)
                .background(Color(.systemBackground))
                .border(Color.gray.opacity(0.3))

            VStack {
                Text("Current Value:")
                    .font(.headline)
                Text("\(value)")
                    .font(.system(size: 36, weight: .bold))
                    .padding()
            }
            
            Spacer()
        }
        .padding()
    }
}

#Preview {
    VerticalScrubberPreview2()
}