I am sorry but the interface I sent you is with identical number of faces in both interfaces. The cylinder is not distorted but what I am starting to suspect for the left handed faces is that the cylinder is not a perfect cylinder so while it moves in some points it penetrates with the stationary interface. 

The interface consists of both structured and unstructured cells because the cylindrical interface is enclosing an archimedes screw and it wasnt possible to create a structured volume mesh in all locations inside the cylinder.