Air Purifier Indoor AQI does not go down to Healthy

I have 3 units, 1 unit AQI does not update or return to healthy levels after running for hours. I have to turn it off, reset, delete, add it again to the app. Work normal until AQI rises. Changed filter, cleaned unit, moved to another room no fix. Wyze support is terrible as usual and said power it off and on duh.