Redwood Guy - my first thought, which I'm sure you have had also, would be to check for dirt being carried into the constrictor. If you are going from full out to full in a lot and the cord is coming into contact with a redwood or webbing that is in contact with a redwood, then the cord could be picking up a lot of debris from the bark and carrying that into the constrictor.
In my experience redwood bark has a lot of "dirt" imbedded in it. That would foul the constrictor and quickly cause a "jam". Small dirt particles can foul anything that relies on two parts sliding against each other.
Also, if the rope is picking up any sap and carrying that into the constrictor, then the sap is going to act like glue and "jam" the constrictor.
Just my first thoughts.