Map in SwiftUI just wont follows users heading when first shown

I want to use a Map to show current location and heading, but the map first show, it just wont work. And when I switch off and switch on again, it works. codes below:

BackgroundMapView.swift

import SwiftUI
import MapKit

struct BackgroundMapView: View {
    
    var scope: Namespace.ID?
    
    private var cameraPosition: MapCameraPosition = .userLocation(
        followsHeading: true,
        fallback: .automatic
    )
    
    private var locations: [Location]
    
    init(_ scope: Namespace.ID? = nil, locations: [Location]) {
        self.scope = scope
        self.locations = locations
    }
    
    var body: some View {
        Map(
            initialPosition: cameraPosition,
            scope: scope
        ) {
            MapPolyline(coordinates: locations.map({ $0.coordinate.toGCJ02 }))
                .stroke(
                    .red,
                    lineWidth: 3
                )
        }
        .mapControlVisibility(.hidden)
    }
    
}

#Preview {
    MainView()
}

HomeVIew.swift

import SwiftUI

struct HomeView: View {
    
    @StateObject private var locationManager = LocationManager()
    
    @State private var isMapEnabled = UserDefaults.isHomeMapEnabled {
        didSet {
            UserDefaults.isHomeMapEnabled = isMapEnabled
        }
    }
    
    @Namespace private var mapScope
    
    var body: some View {
        if isMapEnabled {
            BackgroundMapView(mapScope, locations: locationManager.locations)
                .mapScope(mapScope)
        }
    }
}