AlertDialog not showing when returning to the app

Question

I'm developing an app with Kotlin and Jetpack Compose.

I have to show an alertDialog after a certain time, everything works fine while the app is in the foreground, but, if the time ends while the app is in the background, when I go back to the app the dialog doesn't appear. Only the faded background is shown but not the dialog, and I can't interact with the app. I noticed that the dialog reappears if I rotate the device, probably because a configuration change is triggered. I just want to show the dialog after a certain time and the time runs even if the app is in the background.

I tested the code below on two emulators (Pixel 2 Api 30 and Pixel C Api 30) and the problem does not exist, while in my real device (Xiaomi Mi A2 Api 29) there is this problem.

This is a screenshot of the app:

If I click the button after some time the alertDialog appears:

but If I click the button and then I navigate out of the app and the time finishes, when I go back to the app, this is the result:

This is the code:

MainScreen.kt

@Composable
fun MainScreen(
    viewModel: MainViewModel = hiltViewModel()
) {
    val uiState = viewModel.uiState.collectAsState()

    Box(
        modifier = Modifier.fillMaxSize(),
        contentAlignment = Alignment.Center
    ) {
        Button(onClick = { viewModel.showDialogAfterSomeTime() }) {
            Text(text = "Show Dialog After Some Time")
        }
    }

    if (uiState.value.showDialog) {
        AlertDialog(
            onDismissRequest = { /*TODO*/ },
            confirmButton = {
                TextButton(onClick = { /*TODO*/ }) {
                    Text(text = "Ok")
                }
            },
            title = {
                Text(text = "Title")
            },
            text = {
                Text(text = "Text")
            }
        )
    }
}

MainViewModel.kt

data class MainScreenUiState(val showDialog: Boolean)

@HiltViewModel
class MainViewModel @Inject constructor() : ViewModel() {

    private val _uiState = MutableStateFlow(MainScreenUiState(showDialog = false))
    val uiState = _uiState.asStateFlow()

    fun showDialogAfterSomeTime() {
        viewModelScope.launch {
            delay(4000)
            _uiState.update { MainScreenUiState(showDialog = true) }
        }
    }
}

Thanks.