Pretty sure smart lock has to be enabled for voice to unlock the phone.. I'm going to play with it a bit at work today maybe factory reset and see if that fixes it...Have you tried with smartlock off? I don't use that and don't have anything at hand that I could use to test whether that combination causes issues but since you mentioned it and you mentioned that the phone isn't actually locked when the screen goes to sleep I'm wondering if the two may be related??? Again related to your smartlock, are you actually talking to the device or are you talking to a Bluetooth device when this happens that just channels through your device?