I made up a spacer to replace the original spacer so that it has a recessed inner ledge/lip. Careful measurements of the recess means that the spacer will lock both the alloy and the steel centre to the drive sprocket once the rotor nut is done up. I did this years ago. But it wasn't to fix a problem, it was to stop a problem in the first place.
IMO the the alloy and steel centre shear because of the whip generated by the rotation>>> inertia and recoil. If you can remove or abate this whip by locking the components so they are effectively a single unit then - in theory - there will be no shear.
I've never seen the magnets come loose or fall out where the steel centre and alloy are intact.
I've never seen or heard of a triple with this issue....because the rotational whip is different/smoother ...120' vs 180' = eliminating or lessening the whip is a good thing.
I've done this on a few twins [after convincing the owners of the benefits or at their request] and none have ever had an issue.