Matchmaking Backfill Not Working – Players Are Placed in Separate Sessions

Summary

There is an issue with matchmaking/backfill on my published island. Players are frequently being placed into new empty server sessions instead of joining existing active sessions that still have available player slots. This has been reported by multiple players, and I have also reproduced the issue myself several times across different days.

Please select what you are reporting on:

Creative

What Type of Bug are you experiencing?

Island Settings

Steps to Reproduce

1- Launch the published island using Public Matchmaking.
2- Make sure there is already an active session with players and available slots.
3-Join the island from another account or have another player queue separately.
4-Complete matchmaking normally.
5-The new player is placed into a separate empty session instead of joining the existing active session.
6-Repeat the test several times.

Expected Result

Players should be backfilled into existing active sessions that still have available player slots.

Observed Result

Players are frequently placed into newly created empty sessions and start alone, even while other active sessions still have space available.

Platform(s)

PC , PS5

Island Code

1345-5145-1363

@Flak