I tried to cure my fletcher in order to get the stick trade to 1 emerald (it was at 5 emeralds) but instead the villager's discounts reset. (Sorry, I don't have a "before" picture for this)

I then tried to recreate the effect with one of my librarians.

Before:

After:

I don't whether this is intentional as a punishment for re-curing but I couldn't find anything on it.

Update: Curing the villagers again doesn't change the discounts.