splitscreen multiplayer: XUID only communicated for first player even if all players have different gamertags

I have a dedicated bedrock server. My family has been playing on it for a year. In 1.21.131, people other than the first player (on splitscreen) are not assigned XUIDs. Here’s a snippet from the server console:

mcbedrock  | [2025-12-20 14:40:15:175 INFO] Player connected: GodOfCheese, xuid: 2653236744757532
mcbedrock  | [2025-12-20 14:40:23:854 INFO] Player Spawned: GodOfCheese xuid: 2653236744757532, pfid: 59B4FDADACEBB36
mcbedrock  | [2025-12-20 14:40:45:865 INFO] Player Spawned: Abigalien xuid: , pfid:

Both players are able to join successfully.

The bug is that the client doesn’t seem to be providing the xuids for the other splitscreen players.

The impact of the bug is that the primary SMP player (GodOfCheese in the above example) must ALWAYS be the primary player, or else that player will log in with a new profile (for xuid ““). So, if Abigalien logs in again as the PRIMARY user (instead of GodOfCheese), then Abigalien will receive a newly-spawned character with no inventory, XP, or pets. As if they had never logged into this world before. This makes SMP play for servers essentially unplayable.

My server.properties has msa-gamertags-only=true and online-mode=true.

How can I get my Xbox One X Minecraft client to send the XUIDs for all users currently in the Minecraft game from that console?

Thanks!