the inside of that camera needs to be matt flat black, completely -- otherwise you will get light from the pinhole reflecting off the film and around inside the camera, also off the sides and onto the film.

this cannot be stressed too much -- go buy some of the flattest black matt paint you can find at the car part store -- something that makes things disappear, and spray the inside with that, first covering the pinhole of course. I've done this with Holgas and my Russian stereo camera and it does wonders ...