Exception when shutting c++ app down after using late binding with DAO.DBEngine

Question

This question is a continuation of this issue.

I have some C# code that uses late binding for compacting a database:

public bool CompactAccessDatabase(string strSourceDB, string strTargetDB, string strPassword)
{
    try
    {
        // Get the DBEngine property
        dynamic dbEngine = Activator.CreateInstance(Type.GetTypeFromProgID("DAO.DBEngine.120"));

        // Build the DB connection string
        string strDecryptedPassword = "";
        string strDBConnectionString = "";
        if(!string.IsNullOrEmpty(strPassword))
        {
            if (!DecryptDatabasePassword(strPassword, ref strDecryptedPassword))
            {
                SimpleLog.Log("DecryptDatabasePassword returned false");
            }
            strDBConnectionString = ";pwd=" + strDecryptedPassword;
        }

        // Perform the compact
        dbEngine.CompactDatabase(strSourceDB, strTargetDB, null, null, strDBConnectionString);
    }
    catch (Exception ex)
    {
        SimpleLog.Log(ex);
        return false;
    }

    return true;
}

In itself it is functioning fine. My C++ calling wrapper:

bool CMSATools::CompactAccessDatabase(CString strSourceDB, CString strTargetDB, CString strPassword)
{
    VARIANT_BOOL vbResult = VARIANT_FALSE;

    if (m_pInterface != nullptr)
    {
        CComBSTR bstrSourceDB(strSourceDB.AllocSysString());
        CComBSTR bstrTargetDB(strTargetDB.AllocSysString());
        CComBSTR bstrPassword(strPassword.AllocSysString());
        throw_if_fail(m_pInterface->CompactAccessDatabase(bstrSourceDB, bstrTargetDB, bstrPassword, &vbResult));
    }

    return vbResult == VARIANT_TRUE ? true : false;

}

What I am finding is that when I run my C++ app (x64) in release or debug and I execute this code, whilst it compacts, when I shut the app down I get this exception: Am I missing a step here?