SwiftUI NavigationView title principal item partially obscured after return from subView

Question

I'm trying to use a VStack with two Text items for a centred title. It looks something like this:

When I go to a subView and then return, it looks the same for a moment but then an obscuring bar appears across the top of the upper Text item like this:

This code demonstrates the problem.

import SwiftUI

struct ContentView: View {
    var body: some View {
        NavigationView {
            NavigationLink("Go to Second View", destination: SecondView())
                .toolbar {
                    ToolbarItem(placement: .principal) {
                        VStack {
                            Text("Title Title Title").font(.title).bold()
                            Text("Subtitle").font(.subheadline).padding(.bottom)
                        }
                    }
                }
        }.navigationBarTitleDisplayMode(.inline)
    }
}

struct SecondView: View {
    var body: some View {
        Text("Second View")
    }
}

I've tried moving the .displayMode around and tried the different modes but I want to keep the NavigationView as the more compact .inline version. Short of a solution I'll have to rethink, thanks.