Android: SharedPreferences getStringSet() returns onlu [] or [1] after starting the application

Question

I am trying to use SharedPreferences as a storage for my 'favorite item ids'. I am using this in my Kotlin Android app.

When I call method for storing values into SharedPreferences, I'd like to save Set of Strings. Values are present in the SharedPreferences object anytime I check them in my application. But when I close the app (close the app on background or when app crashes) and then open the app again the content of SharedPreferences is [] if I don't save anything in the SharedPreferences during the app run. If I save something into SharedPreferences close the app and open it once again it loads Set with exactly one element [1].

It seems that anytime I store something in the SharedPreferences using putStringSet() a Set with only one element [1] is written int SharedPreferences after the application crashes or is closed.

I've debugged the app many times, put the debug logs everywhere, but cannot find the reason.

Could anyone help?

I am not sure whether I need some permissions in AndroidManifest or somewhere else?

To make a better picture of the app:

Iam using android Emulator (perhaps it requires some special settings?)

More activities are accessing the same SharedPreferences, basically in one activity I write into it and in the other I read from it.

This method I am using for storing values into SharedPreferences:

fun saveFavorite(id: Long){
    val favorites = sharedPreferences.getStringSet(preferencesKey, setOf<String>())
    favorites.add(id.toString())
    with (sharedPreferences.edit()) {
       putStringSet(preferencesKey, favorites)
       commit()
    }
}

And this method I am using for getting values from SharedPreferences:

fun getFavorites(): Set<String>{
    val favorites = sharedPreferences.getStringSet(preferencesKey, setOf<String>())
    return favorites
}