Custom Dimensions Structures don't spawn after leaving world

Between both versions of 20w28a and 20w29a. I have correct format for custom structures in world. When uploading datapack to server I get this crazy error and i still cannot figure out what causes it. I've tried googling & video searching.

 

Hopefully you can resolve why "datapacks" with custom dimensions / biomes / structures don't load into servers.

Server Error Report:
15.07 20:40:21 [Server] Netty Epoll Server IO #5/ERROR java.io.IOException: Failed to encode: Value 100 outside of range [0:7] gn$b@33e63b90
15.07 20:40:21 [Server] Netty Epoll Server IO #5/ERROR Could not serialize de@39fba46f (class de) - will not be sent to client!
15.07 20:40:21 [Server] Netty Epoll Server IO #5/ERROR Could not serialize de@7a7e3435 (class de) - will not be sent to client!