Upstream has released updates that appears to apply and compile correctly.
This update has not been tested by PaperMC and as with ANY update, please do your own testing
My recent work on serialization is now in CraftBukkit so was able to drop the patch and Paper
is now consistent with upstream.
Bukkit Changes:
e2699636 Move API notes to more obvious location
CraftBukkit Changes:
1b2830a3 SPIGOT-4441: Fix serializing Components to and from Legacy
Use a proper teleport for teleporting to entities in different
worlds.
Validate that the target entity is valid and deny spectate
requests from frozen players.
Also, make sure the entity is spawned to the client before
sending the camera packet. If the entity isn't spawned clientside
when it receives the camera packet, then the client will not
spectate the target entity.
Aikar
Spottedleaf