I've never worked in a Commercial processing - or a "One-Hour" lab ... but...
One of the participants in a Workshop came to me and announced that her camera was now officially a "wreck" and she had to replace it. Knowing that the camera in question was a Canon A-1 and having seen exellent work from it, I asked her how she came to that conclusion.
She had exposed a roll of film, and had it processed at the local Super Market "One-hour" station. There was *no* question that the resulting prints were a disaster. She had complained, and one of the counter-persons (not even remotely worthy of the title "Tech") had (guru from the mountain top voice) adamantly and decisively blamed her camera.
I asked to see the developed film - part of what we were studying was trying to determine quality of processing from the appearance of the processed negatives/ transparencies ...
The film was cut in strips - four or five to a strip - and when laid out in sequence, it looked like a barber pole - diagonal "bands" of alternating under- to over - development. Severe over and under.
Needless to say - NO problem with the camera - the processing crew - was another matter.
I'm still trying to figure out what happened - everyone I've talked to say that it it isn't possible to barber-pole-ize film in a processing machine like that - either deliberately or accidentally.