Sometimes my phone ignores the Ok Google command. I've noticed that I need to say it in the exact same way, as I said it during the voice model retraining. Even a wrong distance between my mouth and my phone's microphone can cause it to ignore the OK Google command.
Is there a way to save many voice model profiles just like you do it with fingerprints? In android 6.1 you can save up to 5 models of your fingerprint, all of them are checked during the fingerprint authorisation.
If I could record more than 3 "Ok google" commands during the voice model retraining, I think it would work much better.