Thanks for sharing your observations Francis. Probably Montblanc decided to punish those who fiddle with their pens. Tamper evident.
Btw even the older design was very prone to case feeder collar breakage. Mb never reused the case feeders, always replaced them. The best design was on the celluloid era case feeders.
Unfortunately I expect you are right Hari.
Avoiding tampering is probably also the main raison why MB altered the position of the removal slots from 180 to 120 °. And I agree, also the flanged nib housings of the older design are sensible fo breakage;
But finding a replacement nib housing is not as problematic as re-glueing the broken off ring back on the partly broken off section collar.
And you are right again when stating their optimum nib housing design was as on the celluloid pens of their golden era.