First of all I'm an android player, so I started a new game, when I created the character I put the buxom perk on it, I was exploring normally for a while, without using any transformation up to that point, nothing strange happened either, after getting enough money I bought Bovum Sherry and treated it alchemically to enlarge my breasts, when I got to a point I saw that it didn't grow as expected and I checked my character, finding that I no longer had the buxom perk, I tried to go back to a much earlier autosave, but the problem was already present at that point, I'm going to play the save in case it helps you to know how this bug happened.