@123: When he says “turn on the fan”, Google Assistant sees “Turn on” then tries to match a device or scene to the rest of what was said. In this case “[the] fan”. Then it finds two scenes “Turn on Fan” and “Turn off Fan” and it runs both.
Using keywords in the names of entities isn’t a good idea, I guess
I use an IR blaster to control my air conditioner, and had similar problems with managing state. I added an Sonoff S31 smart plug to monitor the energy used by the AC. If the energy draw is more than 3 watts, it is assumed that the AC is operating and the state is set to ON.