setAlarmClock is not exact

Question

This is my first question on stackoverflow. I have read many similar topics but have been unable to find the problem and I am getting a bit desperate.

I develop an app with an alarm clock. This alarm clock only rings under certain circumstances. If they don't apply, I send a notification to the user and set the next alarm 10 minutes later using setAlarmClock(). If the conditions don't apply until a user specified time, the alarm never goes off.

Now when I leave the phone unobserved for a while and check the notifications, I see that they didn't come in every 10 minutes, but very irregularly. Sometimes it came after 10 minutes, other times 11, 15, 30, or whatever.

The problem only occurs when the phone is not plugged in, and so I figured it has something to do with Android's doze mode. setAlarmClock() should help with this problem but it doesn't. I also tried setExactAndAllowWhileIdle(), but that didn't work either. So if anyone has any idea what the issue might be, I would be really greatful to hear about it.

This is my code: First, the two methods inside my AlarmController

//this is called the first time an alarm is set
public void registerAlarm(int id, AlarmClock alarm) {
        if (alarmManager == null)
            alarmManager = (AlarmManager) ctx.getSystemService(Context.ALARM_SERVICE);

        Calendar alarmTime = alarm.getAlarmCalendar();

        //create alarm intent
        Intent intent = new Intent("START_ALARM");
        intent.putExtra("alarm_id",id);
        PendingIntent alarmIntent = PendingIntent.getBroadcast(ctx, id, intent, 0);

        AlarmManager.AlarmClockInfo info = new AlarmManager.AlarmClockInfo(alarmTime.getTimeInMillis(),alarmIntent);
        alarmManager.setAlarmClock(info, alarmIntent);
        //alarmManager.setExactAndAllowWhileIdle(AlarmManager.RTC_WAKEUP,alarmTime.getTimeInMillis(),alarmIntent);
    }

// This is called if the conditions didn't apply
public void registerSnoozeAlarm(int id, int minutes) {
        if (alarmManager == null)
            alarmManager = (AlarmManager) ctx.getSystemService(Context.ALARM_SERVICE);

        long alarmTime = System.currentTimeMillis() + 1000*60*minutes;

        //create alarm intent
        Intent intent = new Intent("START_ALARM");
        intent.putExtra("alarm_id",id);
        PendingIntent alarmIntent = PendingIntent.getBroadcast(ctx, id, intent, 0);

        AlarmManager.AlarmClockInfo info = new AlarmManager.AlarmClockInfo(alarmTime, alarmIntent);
        alarmManager.setAlarmClock(info, alarmIntent);
        //alarmManager.setExactAndAllowWhileIdle(AlarmManager.RTC_WAKEUP, alarmTime,alarmIntent);
    }

The Receiver in the manifest:

<receiver android:name="packagename.AlarmReceiver"
          android:exported="false">
          <intent-filter>
              <action android:name="START_ALARM" >
              </action>
          </intent-filter>
</receiver>

This is my AlarmReceiver:

public class AlarmReceiver extends WakefulBroadcastReceiver implements Observer{
    private Context context;
    private AlarmClock alarm;
    private Intent intent;

    @Override
    public void onReceive(Context context, Intent intent) {
        this.context = context;
        this.intent = intent;

        //request data from server
        Bundle extras = intent.getExtras();
        int alarmID = extras.getInt("alarm_id");
        alarm = DataHandler.getInstance(context).getAlarm(alarmID);
        DataHandler.getInstance(context).requestDataForAlarm(alarm,this);
    }

    @Override
    public void update(Observable observable, Object data) {
        Measurement measurement = (Measurement) data;

        if (*someConditionapplies*){
            //play ringtone
            AlarmSoundController sc = AlarmSoundController.getInstance(context);
            sc.playSound(alarm.getAlarmSoundPath());

            //send a notification message
            ComponentName comp = new ComponentName(context.getPackageName(), AlarmNotificationService.class.getName());
            intent.putExtra("alarm_id",alarm.getId());
            intent.putExtra("description", alarm.getDescription());
            intent.putExtra("data", measurement.getData());
            startWakefulService(context, (intent.setComponent(comp)));
            setResultCode(Activity.RESULT_OK);
        }
        else {
            //if user specified end time is reached, send final notification, else try again in 10 minutes

            Calendar alarmEndTime = alarm.getAlarmEndCalendar();
            Calendar now = Calendar.getInstance();

            if (now.before(alarmEndTime)) {
                //schedule new alarm in 10 minutes
                DataHandler.getInstance(context).registerSnoozeAlarm(alarm.getId(),10);

                sendNoAlarmNotification(measurement, false);
                setResultCode(Activity.RESULT_OK);
            }
            else{
                //send the last notification message
                sendNoAlarmNotification(measurement, true);
                setResultCode(Activity.RESULT_OK);
            }
        }
        DataHandler.getInstance(context).removeObserver(this);
    }

    private void sendNoAlarmNotification(Measurement measurement, boolean lastNotification) {
        ComponentName comp = new ComponentName(context.getPackageName(), NoAlarmNotificationService.class.getName());
        intent.putExtra("alarm_id", alarm.getId());
        intent.putExtra("description", alarm.getDescription());
        intent.putExtra("wind", measurement.windAvg);
        intent.putExtra("last_notification", lastNotification);
        intent.setComponent(comp);
        startWakefulService(context, intent);
    }
}

Thanks a lot in advance!