Another possibility is light striking your negatives during the development process, if you claim that the problem continues beyond the frame.
It is not logical to assume a light leak in the camera if there is only one instance of it on a roll of film.
Other people learned from the internet to chant "CLA" whenever something is wrong. Aside from the fact that most of them don't really know what a "CLA" entails, you should rarely, if ever, have one performed on your cameras.