The Zombie in my iron farm despawns even though it has a name tag. How do I stop this?

[Da_Jiff6]

Something weird is going on. The zombie is protected from the sun, has a nametag, and no iron golems can get to it. For some reason it is still despawning. I know minehut is strict about any form of exploit in the game, but an iron farm should work. We really need this farm for building, emeralds, and hoppers. We can't do nearly as much without it. If there is anything i can do to prevent this that would be good to know.

The zombie sits on top of a composter with a single trap door above his head. He is suspended above the water trails that lead to the killing chamber of the farm. The zombie has never left this area in all the time we have used this farm.

[_Tarna_]

This was from an old post but according to google, it says this

"A monster which has been named with a name tag will despawn if players log out more than 100 blocks from them. However, one created from a renamed spawn egg will despawn as normal. If a monster is holding any items or wearing any armor that was given by a player or picked up from the ground, it will not despawn."

If its not that, it could just be an issue with paper, the server software Minehut runs on, but I have never seen someone with this specific issue before.