The 4216 error that occurs during World play occurs when there is an error in the server code you created.
- Please try to find the error in your onCreate / onJoin / onLeave or Message Event and fix it.
- It is recommended to use Nullable or try-catch syntax to resolve issues with code stability and exception handling.
Please check the caveats for writing server code.
Please refer to the following guide [Precautions when using server code]