There is a perception that film is always static. (Steady.) That is not always the case.
In dealing with moving film for fifteen years, I have learned that the idea of film always being flat isn't necessarily true. When cinema film is projected, we often have the perception that it lies flat in the gate and it always stays straight and true. Yes, it needs to run straight and true as it moves through the projector but, in reality film projection is a very dynamic process. The film does buckle, jitter and weave as it it advanced through the machine but the trick is to make sure that it buckles, jitters or weaves into exactly the same position each time the projector's shutter opens. As long as the viewer's eye (visual system) acquires a congruent image, frame to frame, he will perceive it as being steady and in focus even when it isn't.
In my hyptothesis, if the film was moving as it was advancing from one frame to the next, as it was being wound and rewound through a camera or if it was being loaded into its cartridge, the patterns of light and dark areas on the film could change. If the camera's sprockets were pushing against the film, it could cause a slight buckling around the sprocket holes which would cause the patterns to appear different.
In fact, when diagnosing projector problems, a good technician should look at the sprocket holes of the film to see if there is any damage. A malfunctioning movie projector will cause permanent damage to the edges of the sprocket holes but, even if it is not, there is still stress to that area.
In a still camera, there are pressure plates and different arrangements of the film aperture ("gate" or "trap" in the cinema world) which hold and transport the film differently but I still think it isn't always true to think that film is always static, regardless of whether it is a still camera or a cine camera.
While I do agree with your theory that this could be caused by some form of triboluminescence or or mechanoluminescence, I also see evidence that the markings were caused as the film was moving. I think our theories mesh in these respects.