Sadly me and my friend already update our old realm to 1.18.12.01 since they said they fix entity not save in chunks related to mobs disappear issue but fed or tamed wild mobs are still disappearing and i think the movement of the entity that save from the game is not reload well especially the entity that moves alot like axolotl and tropical fish they keep disappearing than the other land mobs hoping it wont happen to allay mob which is in air and very rare..