ı got a mending villager after that ı slept 1 night then ı checked my vıllager to buy mending but it was now selling fire aspect 3 ınstead of mending (im on singel player)

ı expected to get my mending book but ı couldn't

what actually happend here is ı slet one night and my mending villeger is gone and this thing happend half of my villagers

Steps to Reproduce:
1. get a villager and make him librarien

2. get mending but dont buy it
3. sleep 1 night