I know what you mean about the blend door. The one on my wife's Windstar van failed but it was the blend door itself that broke, not the actuator. Ford trucks and vans are imfamous over this one.
HOWEVER - as you pointed out yourself, the heating and dash AC on your Class A Sea Breeze is made by Evans, not Ford, so it is a different system. Not sure that there are any Ford parts involved. If not, then it is a good thing!
A Ford powered Class C would be fully Ford and subject to the blend door troubles.