hi, if on the RHS of the picture, the shutters are "capping". I guess that the first shutter is stopping about 2/3 across the film aperture. On some attempts, it looks like it stays there until the second curtain hits it, when they both complete the journey together. Given the shape of the light streak, I would say that the first curtain metal edge is catching something in the top curtain channel before being released. If you cannot see anything wrong in the shutter test at all the usual shutter speeds, perhaps this problem has cleared. You could load another film. This time (you should always do this with an unknown camera) fire a few frames with the lens covered. If you see marks on these pictures, you can be quite sure that they are caused by light leaks.
Good luck.