The bottom end of the channels the film slides into in the septums is crimped a little bit to grip the film. Thru age, this crimp can become loose. If you look closely you can see these crimps, and thru the delicate use of a pair of pliers you can apply a little more crimp if the film sheets slide out without friction.
Prmiarily you will find that it is possible for a sheet to partially slide out, when you transport the grafmatics, and then when you go to use them, you end up bending, scratching or crumpling a sheet of film that has partially slid out of the septum.