I've created a villager breeder this morning using this video in minecraft 1.16 java edition.
Everything seems to work correctly (the beds assignments are right, the farmer throws his excess to the others villagers).
But my villagers don't breed. I see heart particles at least 1 time a day but they always end up with storm particles. (when I say always I mean about 10 times in a row)
I don't know if I'm just not lucky or if there is an issue with my villagers. (and I accidentally hit my villagers so I don't know if this could influence their breeding rate but if it does feel free to tell me).