Ah... I know it shows each time you get a notification (supposed to eventually stop for that single notification after some time passes) or if the notification keeps resetting itself. I have do not disturb setup on mine so mine stays dark all night except the screensaver clock.
In order for it to trigger via the sensor an object has to be pretty close. I can't trigger mine with my hand or any other object more than a foot away from the sensor. Does your fan happen to sit on the stand or is close enough to cause the stand to vibrate (or when/if its oscillating?)? Mine triggers on vibrations pretty easily. Lastly, (I must ask, lol) is there anything interfering with the sensor (screen protector missing the cutout)?
Having said of all of that I went and tested it out for myself thinking no way air could trigger the sensor. I stand corrected. I have a pedestal fan that sits 1 foot away from my nightstand and ~3 away from my phone. To my surprise the fan at full blast pointed directly at the phone triggered active display like crazy. Fan at a medium setting about the same, and at lower setting slightly less. Turning the phone away from the wind still triggered AD, but less often in all 3 speed settings. Blocking the wind from hitting the phone stopped AD from displaying abnormally. At night I place my phone on my old tylt vu charger, but my fan doesn't point directly at my phone (minimal wind from my fans).