When I play ClientSim in the world project, I get the error in the attached image and ClientSim does not work. This may not occur immediately after starting Unity, but it did occur on the second and subsequent playback.
This can occur even if there is no PlayerObject or Enable Persistence component in the world.
This phenomenon was observed in VRCSDK 3.7.4 and VRCSDK 3.7.3-Persistence-beta.