A build check error in the area "Realtime conformance". An error: the game cannot be published until it is fixed.
The build check runs on every game LobbyLab builds, and each problem it finds has a stable code, the exact message, the file and line when it names one, and a link to this page.
What the check looks at
Realtime games get a simulated match: every player joins, the host starts, smoke intents and inputs play for about 6 seconds of ticks, and one player disconnects and comes back. tick must be synchronous, total and within its time budget.
How to fix it
Keep tick cheap and total, return plain JSON under the size limits (state 256 KB, a view 32 KB per frame), and never end the session when a match ends.
See also: every error code, the API reference and the docs.