Meta user leaving a group rejoins (race)

[jtagcat]

1. Group chat. User B is a (meta-housed) member.
2. User B leaves the group.
3. Event is bridged: User B's Matrix representative leaves Matrix room ("origin_server_ts": 1716217888116, "age": 14121729,).
4. FB bot invites User B's Matrix rep. The rep joins.
5. User B sends a notice: User B left the room ("origin_server_ts": 1716217887935, "age": 14119550 (older))
6. User B rep is kept in Matrix room, even though they are not in the group (on Meta side).