GeneratedStructures loosing their PDC sometimes

Expected behavior

PDC keys should stay on the generated structures

Observed/Actual behavior

Sometimes, with no (at least for me) repeatable pattern, GeneratedStructures just.. loose their PDC keys completely.. I dont know why or how..

For now though, I seem to observe it mostly on Pillager Outposts and Monuments.. That could be a coincidence though.

Steps/models to reproduce

Well.. Save a key on a GeneratedStructure.. Idk.. Restart the server?
I really don't have any repeatable pattern..

Plugin and Datapack List

Happens without any Datapacks and just my own plugin that sets a PDC value and reads it.

Paper version

[18:19:15 INFO]: This server is running Paper version 1.21.10-115-main@af06383 (2025-11-21T23:42:01Z) (Implementing API version 1.21.10-R0.1-SNAPSHOT)
You are 2 version(s) behind
Download the new version at: https://papermc.io/downloads/paper
Previous version: 1.21.10-113-9fc21bc (MC: 1.21.10)

Yes, 2 behind because of pre-release.

Other

No response

The report names no source file, test, or entry point and has no repeatable reproduction. Begin by checking whether restarting a Paper 1.21.10 server after saving a PDC value reproduces the loss on generated structures; done means identifying a reliable trigger and preserving the PDC keys with a regression test.