I disagree. The sellita is designed like the ETA. The main spring's bridle is designed in such a way that it can't be over wound. Also most of our reps (if not all) that have a screw down crown have a clutch mechanism in the crown which prevents the movement form being hand wound when you screw down the crown.
So the ratchet can't break? Sure it can! IMO only two things can cause it.
1. Metal fatigue, read: poor production/ quality. Judging from all the complaints this most likely is the case.
2. Broken or malfunctioning main spring bridle due to rust or lack of proper grease.