How old is your "new" RB? What model is it (Pro, Pro S, Pro SD)? I have a Pro SD with 3 Pro SD magazines and have never had this problem, however it seems to be systematic to the two magazines you have. Slightly excessive spacing between two frames is of course a problem that is easy to live with, while 4 stops overexposure is not going to give the best quality and is also an easy problem to fix. Did you use a lens hood for the shots wth the bleed? This could well help stop light bouncing off the inside walls of the camera and reaching the film from an odd angle.
Regards,
David