I had problem with the session host migration.
Create a session then other player joined and the session host leave the session the host switched to the other player but if the left player tried to join back I get this error
SessionException: An item with the same key has already been added. Key: yRjdbH7OX9xcfulRe6HbKXXForOi
the key is the player Id
the exception comes from this lien
this is in the LobbyPatcher class
I am using the Multiplayer Service and relay and distributed authority on unity 6 0.27f
and have the Unity transport 2.4.0
NGO 2.1.1
Multiplayer Services 1.0.2