Crash when SAFE_RELEASE is called on IMMDeviceEnumerator

I am using a service to detect the connection of head set. When the microphone is connected and disconnected, I am getting notification. The thing is, when I end the service manually, I am facing a crash in the service while doing SAFE_RELEASE. Here is the code...

NotifyHandsetConnectionStatus::NotifyHandsetConnectionStatus() : _cRef(1), _pEnumerator(NULL){}

NotifyHandsetConnectionStatus::~NotifyHandsetConnectionStatus()
{
 //   SAFE_RELEASE(_pEnumerator)
    if (_pEnumerator)
    { 
        _pEnumerator->Release(); // CRASH
        _pEnumerator = NULL;
    }
}

void NotifyHandsetConnectionStatus::Init(DWORD threadID)
{
    PTTThreadID = threadID;
    HRESULT hr = S_OK;

    CoInitialize(NULL);

    if (_pEnumerator == NULL)
    {
        // Get enumerator for audio endpoint devices.
        hr = CoCreateInstance(__uuidof(MMDeviceEnumerator), NULL, CLSCTX_INPROC_SERVER,
            __uuidof(IMMDeviceEnumerator), (void**)&_pEnumerator);
    }

    if (hr == S_OK)
    {
        _pEnumerator->RegisterEndpointNotificationCallback(this);
    }
}

and here is the class declaration...

class NotifyHandsetConnectionStatus : public IMMNotificationClient
{
    LONG _cRef;
    IMMDeviceEnumerator *_pEnumerator;
    DWORD PTTThreadID;
public:
    NotifyHandsetConnectionStatus();
    ~NotifyHandsetConnectionStatus();

    void Init(DWORD threadID);
    ULONG STDMETHODCALLTYPE AddRef() override;
    virtual ULONG STDMETHODCALLTYPE Release() override;
    HRESULT STDMETHODCALLTYPE QueryInterface(REFIID riid, VOID **ppvInterface) override;
    HRESULT STDMETHODCALLTYPE OnDeviceStateChanged(LPCWSTR pwstrDeviceId, DWORD dwNewState) override;
    HRESULT STDMETHODCALLTYPE OnDeviceAdded(LPCWSTR pwstrDeviceId) override
    {
        return S_OK;
    }
    HRESULT STDMETHODCALLTYPE OnDeviceRemoved(LPCWSTR pwstrDeviceId) override
    {
        return S_OK;
    }
    HRESULT STDMETHODCALLTYPE OnPropertyValueChanged(LPCWSTR pwstrDeviceId, const PROPERTYKEY key) override
    {
        return S_OK;
    }
    HRESULT STDMETHODCALLTYPE OnDefaultDeviceChanged( EDataFlow flow, ERole role, LPCWSTR pwstrDeviceId) override
    {
        return S_OK;
    }
};