I found that by putting too much casing on the tube, it tends to dry up and doesn't slide off the tube as smoothly after you use up about half the casing.
Edit: This is with a crank operated cylindrical stuffer.
I saw a hydraulic driven stuffer in a meat processing shop that would fill a 20 foot casing in less than 15 seconds, very fast. In that situation, the casing doesn't have time to dry out and it slid off the tube very easily.
They had a long stainless table, and one guy would run with the tied off end of the casing to the far end of the table as it was being filled; another guy was operating the stuffer and guiding the casing off the end of the tube.