Why not take a micrometer-caliper and measure the actual overal (film plus paper) thicknesses of all the film types you used.

Further the periodicy? of the scratching is something to be looked at. Were those images exposed at once or stayed the film in the camera for some time, which could have induced some certain settings at the rollers? Due to stiffeness this might result in certain kinks in further transport.
Just guessing.