Sorry, just now read you first post for a second time, more mindful this time... You have it about stress marks going over the strip crosswise from hole to hole.
These are kinking marks.
We had a similar case here within the last year. But I forgot how we solved the cause of that, maybe I find that thread again.
The most obvious reason would be if the film would have been put on the spool in wrong orientation, thus entering the mouth of the cassette under a 90° angle, causing stress marks at the weakest location crosswise, where the holes are. But with you being used to bulk loading, this seems unlikely to have happened.