Mobs with armour and name tags dispawn

So I’ve started a really dope minecraft project for my survival world and it was trapping mobs with full diamond armor in cages ( pretty stupid am I ) and I’ve dropped them enchanted armor that they picked up and I even named them with name tags but one day when I come to see them one of them DISPAWNED even with the armour and name tag and so I just closed the app and restarted it thinking it was like a visual bug but when I re join the mob is still missing and A OTHER FULL DIAMOND MOB DISPAWNED TOO . Plz fix this issue it’s not fair I keep losing stuff for mobs that can’t even stay and keep dispawning even with given armor by players and name tags .