Minecraft 1.16.5
Forge 36.1.15
Quark-r2.4-312

I've had this problem for months now, where a single frog will keep trying to replace the only frog on the server. Is there something I can do to stop this? It's happened on several different versions of Quark, and at least two different versions of Forge. I keep using the /kill command to remove it, but it keeps coming back.

[Server thread/WARN] [minecraft/ServerWorld]: Trying to add entity with duplicated UUID 82b6eabe-7a9d-42fb-9986-6781ff04b0dd. Existing quark:frog#88827, new: quark:frog#88827

we have also been having this problem since upgrading to 1.16. i just figured that was a thing that i didn't understand.

[16Jun2021 20:53:01.769] [Server thread/WARN] [net.minecraft.world.server.ServerWorld/]: Trying to add entity with duplicated UUID 83b19f63-5aaf-4d2f-b8bd-c7277b759fc4. Existing quark:frog#818908, new: quark:frog#818908

if it would be of any help, i'd be happy to invite you to my server for testing purposes.