System is working , but defrost damper drives open to about 15-20 degrees when the unit stops running, which allows (outside winter cold or summer hot) unfiltered air to come into the house through this opening , it seems to me the defrost damper should be closed when not being used does anyone Know,I tried to adjust but shaft on the damper has a flat spot that the allen screw keeps putting it back into the same position. Link below my unit is the first diagram HR200B
https://customer.honeywell.com/resources/techlit/TechLitDocuments/68-0000s/68-0171EF.pdf
https://customer.honeywell.com/resources/techlit/TechLitDocuments/68-0000s/68-0171EF.pdf