UPDATE: As it turns out, roll number 6 has little or no fogging. I took 5 rolls with me on my outbound trip and bought the rest at my destination and I'm developing in chronological order. So Frankfurt may not be the culprit after all. It doesn't make sense because I go through the Nice airport regularly, and although they will not hand-check, I've never noticed any degradation. Perhaps it's the combination of both scanners.
The negatives are dense. The image retrieved by the film scanner is low-contrast and grainy.
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Below:
Left = normal negative
Right = fogged, from this trip
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