The Morrison uses a plastic internal ring gear on a pressed steel mounting. That mounting bolts onto something not shown in the picture, but which is probably a steel web-plate and hub. The only problem it is likely to give is if some foreign body, or or perhaps a rather large overload, destroys the plastic ring gear. The Scott Bonnar Diplomat used a far less serviceable design. Here is a picture of the ring gear, from another thread:
[Linked Image]

As you can see, the SB version made the internal ring gear, its drive web, and part of its hub in a single nylon moulding, which was moulded onto a steel inner hub. Drive was transmitted between outer (plastic) hub and inner (steel) hub by knurling on the outside of the steel hub. The problem was that the outer hub was not nearly thick enough radially, and the result was radial cracks in the plastic as it strove to transmit the driving torque, which the knurling on the steel inner hub converted into a bursting load on the plastic outer hub. The hub in the picture had developed quite a number of radial cracks in the outer hub, one of which had propagated to the web, and right across the web and ring gear. Loss of drive occurred when the various cracks in the outer hub cumulatively enabled it to expand enough under load, for the outer hub to slip around the inner hub without rotating it. I haven't heard of a Diplomat plastic gear having lost drive due to a failure of the ring gear part: it is always the failure of the outer hub allowing it to spin around the inner hub, or the long cracks across the web which eventually form, propagating circumferentially and leaving the web in two separate pieces, with the hub isolated from the ring gear. I'm not sure the latter case has ever actually happened, however: some people break the web while struggling to remove the gear and its hub from the axle, and in some cases may think that fracture was already present.