May I ask you something

[DanteAndroid]

I use retrofit with okhttp. And following interceptor:

public class SaveCookiesInterceptor implements Interceptor {
    private static final String TAG = "SaveCookiesInterceptor";

    @Override
    public Response intercept(Chain chain) throws IOException {
        Response originalResponse = chain.proceed(chain.request());

        if (!originalResponse.headers("Set-Cookie").isEmpty()) {
            HashSet<String> cookies = new HashSet<>();
            cookies.addAll(originalResponse.headers("Set-Cookie"));
            SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(App.context);
   //         if (sharedPreferences.getStringSet("cookies", null) == null) {
                Log.d(TAG, "intercept: " + cookies.toString());
                sharedPreferences.edit()
                        .putStringSet("cookies", cookies)
                        .apply();
  //          }
        }

        return originalResponse;
    }
}

...
public class ReadCookiesInterceptor implements Interceptor {

    @Override
    public Response intercept(Chain chain) throws IOException {
        Request.Builder builder = chain.request().newBuilder();
        Set<String> preferences =
                PreferenceManager.getDefaultSharedPreferences(App.context).getStringSet("cookies", new HashSet<String>());
        for (String cookie : preferences) {
            builder.addHeader("Cookie", cookie);
            Log.d("OkHttp", "intercept read Header: " + cookie); // This is done so I know which headers are being added; this interceptor is used after the normal logging of OkHttp
        }

        return chain.proceed(builder.build());
    }
}

...
            instance.client = new OkHttpClient.Builder()
                    .cookieJar(cookieJar)
                   .addInterceptor(new ReadCookiesInterceptor())
                   .addInterceptor(new SaveCookiesInterceptor())
                   .addInterceptor(interceptor).build();

Here is the problem:
I emulate login a website, it succeeds, but then I request my profile page, the response is the login page. After some trys, I add if (sharedPreferences.getStringSet("cookies", null) == null) { in SaveCookiesInterceptor. Then everthing works good.
So what happened in earth? Thx for your time in advance.