I’ve got the google assistant integration set up with my personal GCP account. Whenever I change the state of a device in the google home app (for example turning on a light), it shows on for a second, then shows off. When I refresh the app, it shows on, as the light is supposed to be. When it’s in this “fake off” state, I can toggle it “on” and “off” again to actually turn the light off, but then it shows in the app as if it’s on.
I had this issue once. I’m not 100% sure since it was years ago, but I think I solved it by setting report_state: true in the configuration. Google Assistant - Home Assistant