How did this happen? Light region on film

[Vonder]

36-exp roll of Neopan 400, developed in Xtol. Two of the negatives have a dark/light region. Is this from a camera light leak?

 

[Lee L]

Which direction does the shutter run relative to the frame? If it's vertical, it could be that one curtain is sometimes catching as it travels, pulling the edges of the shutter opening closer together for the remainder of the frame, consequently giving less exposure.

Lee

 

[Kino]

Looks like the tape from the end of the roll might have settled on the image. See how the edge of the density streak is sharp but jagged? Looks like torn tape to me.

 

[Alex Bishop-Thorpe]

Could you show us the full frame? Is it a line along the length of the film, or the width? Is it at the start, middle, or end of the roll? What camera are you using? At least your fault is nice and neat, narrows it down a fair bit...tape seems possible.