Sotah 25: What's the Good of Warnings?

Two dilemmas relate back to the very long mishnah: 1. If a woman violates some aspect of modesty standards or practices, does she get a warning before she loses her entitlement to her ketubah? 2. What about the prohibited marriages - do they get warned, once we know they're not going to drink and also won't get their ketubot? The Gemara suggests several explanations for these dilemmas, still coming off the mishnah. Also, the nature and effect of the warnings - how it protects the women, and when they can be retracted (and when not - how subjective are they allowed to be?).