Zombies despawning in Boats plus having a nametag

So this issue has happened for a while and I havent made tickets about it but I usually build the same Iron farm every single player survival world. It is a small one and requires 1x Zombie in a boat. 

 

This farm is made underground so 0 light from the sun can get to the zombie. no other mobs can get to the zombie either. I have the zombie sit in the boat close to the villagers to scare them. I also put a nametag on the zombie just to make sure it doesnt despawn. But since the release of 1.17 zombies will despawn after 2-3 minecraft days. I am sometimes travelling and go far or go in and out of the nether but that should not make the zombie despawn if it is in a boat and nametagged. according to you guys doing that, is 100% likely to keep the zombie in place and not despawn. Can you please look into this as this is an ongoing issue and I would have to change the way I build farms as well as hoping the next farm will keep the zombie in place.

 

This is an issue on single player as well as multiplayer on Java edition.