Film Streaks Mystery

For the past five years, I've occasionally notice vertical banding in some of my Velvia films.

Please click on the image for better detail.

Here is what I have tried to do to eliminate the issue:

a) I've tried different labs for processing, and still get the same results.

This has led me to believe that it is either x-ray damage, film manufacturing damage, or the camera is at fault (possible light leaks or unevenness of film in the back of the camera), or filters in front of the lens?

b) I get the streaking problem with my Mamiya 7II camera, and also my Hasselblad, so I feel that rules out the actual camera body. Which baffles me, because it appears to be on the same area of the frame!

c) My lab has looked at the films and states that it's not x-ray, because it would also be evident on the dark parts of the film and it is usually a wavy streak going across the film anyway. So that rules out x-rays. I've never had any issue with x-rays ever. I've had some film in my bags over multiple trips and multiple x-rays and never seen any fogging or streaks like this.

d) This has led me to think it might be manufacturing issues with the batch of Velvia I have. I have looked at all my images since I returned from Cappadocia, and around 10% of them are damaged. I looked at my film stock and determined that I have a small batch of film left from around 3 years ago - when Fujifilm kindly sent me a lot.

I've decided to use the newest batch of Velvia I bought just before Christmas, for the next while to see if this eliminates the issue. But in the meantime, I would like to hear from you if you have had similar results with your films, particularly with Fuji Velvia.