Component used: Navigation
Version used: 2.8.1

@Composable
internal fun App() = AppTheme {
    Column(
        modifier = Modifier.fillMaxSize(),
        verticalArrangement = Arrangement.Center
    ) {
        val navController = rememberNavController()
        val innerNavController = rememberNavController()
        NavHost(navController, startDestination = "first") {
            composable("first") {
                //val innerNavController = rememberNavController()
                NavHost(innerNavController, "nested1") {
                    composable("nested1") { Text("nested1") }
                    composable("nested2") { Text("nested2") }
                }
            }
            composable("second") { Text("second") }
        }
        Button(onClick = {
            navController.navigate("second") {
                popUpTo("first") {
                    inclusive = true
                    saveState = true
                }
            }
        }) {
            Text("second")
        }
        Button(onClick = {
            navController.navigate("first") {
                restoreState = true
                popUpTo("second") { inclusive = true }
            }
        }) {
            Text("first")
        }
    }
}

Steps:

navigate to Second
navigate to First there will be an exception:

You cannot access the NavBackStackEntry's ViewModels after the NavBackStackEntry is destroyed.

I move the innerNavController inside composable("first") it fixes the problem.

The problem easy can be reproduced in androidx-main navigation tests:

open androidx.navigation.compose.NavHostTest#nestedNavHostRestore
add composeTestRule.waitForIdle() to the end of the test
run it on a device