Everything keeps disappearing

Mobs keep disappearing. First, my horses keep disappearing. For example, I'll tame a horse and then put it in a pen. I'll turn off my phone and come back to find it completely disappeared. Next, my villagers keep disappearing whenever I encounter them. Currently, I had a villager Breeder set up and all of them disappeared when I went out of the app and went back in. This has been happening for months no