Look what I found on my negs !

First time ever I find this : a piece of film stuck on my negatives. This piece of film does not come from an error or damage that I caused: my developed film is complete, it has no holes or missing parts. So what do you think ? What could be the cause of that : maybe it could be caused by a loading problem of the film into the canister, by the seller ?
I specify that the artifact is between photo 1 and photo 2, so at the END of the film (yes because I used a Canon EOS 300, which unwinds the film entirely before the first shutter).

Photographer:
mackiechartres
Uploaded:
2024-02-26
Camera:
Minolta X-370
Film:
Lomography Lady Grey B&W 400 35mm (available in our shop)
Lens:
Minolta MD Rokkor 50mm 1:1,7
Country/region:
France
Year:
2024
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