Tmax 400, Yashica FX-3. Several frames have these streaks across them. The streak(s) extend beyond the image frame too, but not all the way to the edge.
Looks like you have a shutter problem that needs repair. I don't know the FX-3 but it's unlikely to be anything else unless teh light seals perished on the back, but the leak is the bottom of the frame (neg is upside down in the camera) so it's less likely. Make sure there's not a hair or something trapped in the shutter.
CHeck the seals on the film loading door (and also check that its not warped or distorted) first as they are easy to spot if they are perished or falling apart.
If its a shutter problem that doesn't repond to cleaning, you may want to fire up Ebay for a replacement body, as repairs may well exceed the camera's worth
I notice that, on your specimen print, the sunlight seems to be quite intense and coming from the top right, maybe even catching the edge of the lens or mount (or even a dirty filter glass ). Are the other affected pictures similar?
I have also found that a very bright light source, like the sun, at the very edge of the frame can cause fogging or halation to "bleed" into the rebates, either through internal camera reflections or even within the emulsion/base? Perhaps just check if the negs affected show any similarities in this way before you get too worried by a camera/shutter fault?
I finished the roll in the camera today, and lo and behold, not a single instance of this mysterious "light leak" or whatever it is. The difference? All pics on the latest roll were shot with the standard Yashica 50mm lens that came with the camera. The "light leak" pics were all shot with a Tamron Adaptall-2 lens.
Anyone ever heard of the Adaptall mount light leaking?
Just wanted to be sure there was "closure" to this issue, for posterity.
I examined my adaptall-2 mount and sure enough, it has some bright spots where the underlying silver metal can be seen. This is the source of the mystery streaks - when held at a certain angle these spots were reflecting the sunlight onto the film.