Just a guess but looks like light reflecting off the inside flat surfaces of the camera or film holders. Make sure everything is flat black non reflective inside the camera very close to the film plane. I have noticed this a lot when light reflects off of the edges of a negative holder in the enlarger. That can be solved by beveling the edges of the holder so the reflection does not fall on the negative surface. What you have might be refections off of flat faces of your film holders.