Defects are shown in the crop picture are not straight, just as you specified.
If you look at the emulsion film in reflected light (not direct) emulsion still see? Defects seen in reflected light on the emulsion surface or within the emulsion?
I agree with the hypothesis of mts is a variant.
some sort of debris on the film That Affected Developing.
If you see irregularities in the emulsion in reflected light the fault comes from debris left over from cutting the film emulsion.
If you see fault within the emulsion layer then is another discution.