sometimes some clients get this error InternalReceiveException (in PUN)

sometimes some clients get this error InternalReceiveException (in PUN)
maybe my clients cant join lobby

PhotonNetwork.autoCleanUpPlayerObjects = false;

PhotonNetwork.sendRate = 8;
PhotonNetwork.sendRateOnSerialize = 8; //sendRateOnSerialize는 sendRate보다 낮아야한다!!
PhotonNetwork.BackgroundTimeout = 9.0f;
PhotonNetwork.networkingPeer.QuickResendAttempts = 3;
PhotonNetwork.networkingPeer.SentCountAllowance = 7;


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PhotonNetwork.JoinLobby(new TypedLobby("myLobby", LobbyType.SqlLobby));