Steps to reproduce:
1. Open the attached project: IN-118499
2. Build the Player (Edit > Build)
3. Launch two instances of the newly built Player
4. In both Players go to “Quick Play“ -> “Matchmake“
5. Press '`' button to see the console and observe it

Expected result: Two Players connect to each other
Actual result: Two Players try to connect, then the Host checks for GhostPrefab gets and error: “The ghost collection contains a ghost which does not have a valid prefab on the client! Ghost: '' ('ENTITY_NOT_FOUND').“ and closes the connection. This can be seen in the game console.

Reproducible with: 1.0.0-pre.2(6000.2.8f1), 2.2.6(6000.2.8f1, 6000.3.0b6, 6000.4.0a2)
Could not test in: 6000.0.59f1 (Multiplayer package was not implemented)

Reproducible on: Windows 11
Not reproducible on: No other environments tested

Note: If while launching 2 instances of the Player you get an error saying that only one instance can be launched go to Edit → Player Settings → Player → uncheck “Force Single Instance”.