Steps to reproduce:

Create a new 3D URP project
Go to Window > Multiplayer > Multiplayer Center
Set "Genre of your Game" to Adventure and "Number of Players..." to 2
Change the "Netcode Solution" dropdown to "Netcode for Entities"
Click Install Packages
Once installed, click "Create and open scene with netcode setup"
Enter Play mode and click "Start Host"
Open Window > Multiplayer > Multiplayer Play mode and start "Player 2"
If it doesn't crash after loading, click the "Pause" button in the Editor toolbar to unpause
Observe the Player 2

Alternative reproduction steps for 6.6 (due to change of Multiplayer Center):{}

Open the attached project
Open the "Connection UI" scene
Enter Play mode and click "Start Host"
Open Window > Multiplayer > Multiplayer Play mode and start "Player 2"
If it doesn't crash after loading, click the "Pause" button in the Editor toolbar to unpause
Observe the Player 2

Actual results: "Player 2 unexpectedly stopped" popup appears and Player 2 crashes, Bug Reporter opens

Expected results: Player 2 instance opens and does not crash

Reproducible with versions: 6000.5.0a8, 6000.5.0b9, 6000.6.0a5

Not reproducible with versions: 6000.3.16f1, 6000.4.8f1 (produces errors after 8th step, but the Player 2 does not crash)

Can’t test with versions: 6000.5.0a1 - 6000.5.0a7 (compiler errors when installing packages prevent from entering Play mode

Tested on (OS): macOS 26.5

Notes: