Villagers are despawning

I have been trying to do a survival world and I have done multiple just to see if this is a glitch in that world but all the villagers are de-spawning and I have my world on peaceful so thy cant be dying and I have them in a closed of room and each of them have there own room but they all are just de spawning or disappearing and i don't know if this is a bug or I'm suppose to do something but if this is a bug but if it is please fix it