Stopping an instanced loop is not working

Hello,
first of all I am new to FMOD so this might be a noob mistake:
I am using FMOD in Unity.
I want to instantiate an event that loops an alarm sound. This is happening in the Start() method of a prefab. This seems to work. The alarm is ringing. Once the player reaches to the alarming device and turns it off, the instance should be stopped immediatley. When I turn it off however, the sound doesn’t stop.
The debug messages are printed out correctly though. What am I doing wrong? Here is my starting and stopping code:

private FMOD.Studio.EventInstance alarmSoundInstance;

private void Start()
{
    //Start Alarm Sound
    StartAlarm(alarmSoundInstance);
}

public void StartAlarm(FMOD.Studio.EventInstance instance)
{
instance =   FMODUnity.RuntimeManager.CreateInstance(SoundManager.Instance.MeasurementDeviceAlarmEvent);
    instance.set3DAttributes(FMODUnity.RuntimeUtils.To3DAttributes(gameObject));
    instance.start();
    Debug.Log("ALARM STARTED");
}

public void StopAlarm(FMOD.Studio.EventInstance instance)
{
    instance.stop(FMOD.Studio.STOP_MODE.IMMEDIATE);
    instance.release();
    Debug.Log("ALARM STOPPED");
}

Thanks in advance!

The code you have shown seems fine, it could be simply how StopAlarm() is called in the game. Are you able to get a small Unity project of this happening and send it over for us to test on our end?