i tried a sample .riv file it's look good to me. it's working for me. can you check with your animation?

here is my code and animation.

animation link: https://rive.app/community/files/24532-45875-posture-animation/

import SwiftUI
import RiveRuntime

struct ContentView: View {
    // Initialize the Rive view model with the file name and optionally the artboard
    @StateObject var riveModel = RiveViewModel(fileName: "1animation", artboardName: "soldier selection")

    var body: some View {
        // Display the animation
        riveModel.view()
            .frame(width: 300, height: 300)
    }
}

#Preview {
    ContentView()
}

i seen some difference in your animation can you please check with you animation.