Freezer cold/reefer hot

Took out all shelves and racks. Pulled out plastic cover. Removed screws holding control unit. Removed unit and accresses defrost circuit board. Replacement is in a cover. One screw would not engage so did not put it back in. Reefer was cold within hour of start and is now 1 week after. Unit would start out cold and then warm up before replacement.
Other parts were snap in furnishings that had become damaged with use.