Payload error (log and Google Home)

[hans6910]

In the Home Assistant logs appear errors on the payload (which has to be a string value) committed to the BlindsCommand subject in MQTT.
This error won't prohibit it's functioning, but it should not be there. And it is definitely quite annoying when you've integrated HASS with Google Home. Constantly the blinds function in Google home works, but it gives a reply that the position (a numeric value) is not applicable to this blinds. Even when i change the payload to "open" or "close" it won't fix the problem. How to get rid of this statements in the HASS log and the error reply from Google Home?