You specifically mentioned the magazine, was this only happening with one mag? This doesn't seem like a problem that would involve the magazine at all which is why I'm asking.
I've got a gen4 with no issues, about 2500 rounds through it so far. If you contact Police Ordnance, they are handling the RSA issue in Canada I believe, so they can get you the new recoil spring. This likely shouldn't relate to the direction the brass goes on eject, but its worth having. Otherwise, have you looked at your ejector to make sure its not bent or damaged in any way? Police Ordnance are Glock armourers, so when you call about the RSA issue you can ask their armourer.