Clients dropped from session when server travel

Hello. I am getting the error shown below which appears after a second server travel during the lobby menu.
the client joins the session and so joins the lobby level (Fig.1) → The host makes the session and opens the lobby (Fig.2) → the host loads up the main level after everyone is in (Fig.3) (it breaks here and drops the clients).
I am not sure why the clients are dropped from the session.




Fig.4 – this is the gamemode

Fig.1 and Fig.2 are swapped on accident