Cannot encode packet

[Meledosia]

• This issue is not solved in a development build

Describe the bug
[Netty Server IO #1/ERROR]: Error sending packet clientbound/minecraft:set_entity_data
io.netty.handler.codec.EncoderException: Failed to encode packet 'clientbound/minecraft:set_entity_data'

To Reproduce
Steps to reproduce the behavior:

1. I call for the sleeping pose when a user clicks on a block at a designated location.
2. Code then looks for the Sleeping pose and attempts to apply it.
3. error occurs when the code tries to send the packet.

Expected behavior
Users should see the player laydown. I'm aware that the player "laying down" will still see themselves standing.
Once I get this working, I'll take care of that separately.

Screenshots
NA

Version Info
ProtocolLib-5.4.0 latest off Spigot as of 9/18/25

Additional context
It took days to finally get to the pose enum to even get a serializer. Once I did, I couldn't send it. AI (Co-Pilot) said it was known, but I couldn't find mention of it. If there is a ticket, I'm fine with getting the ticket number and having this request closed. My goal is to get on the "let me know when it's fixed list". Not sure how to connect this to paste bin but I'll attach the dump as a file.

Send Packet Error Dump.log

and a copy of the class (without package) in case it can help or if I screwed up some way.
Copy of class coding.txt