Hi Joe,
The general purpose of Adaptive Defrost Control is to limit the unit going into a defrost mode to only those times when it is needed. This saves on the energy cost of operating the refrigerator/freezer. That means the defrost time is not constant like it happens with a classic electromechanical defrost timer.
It is possible that the problem can be an excessive amount of warm air coming inside refrigerator/freezer causing build up of condensation which freezes up later.
Gene.