The bug has been fixed in Forge 39.0.63. Thanks for your contribution.
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Version: Minecraft 1.18.1 with Forge 39.0.62.
The bug didn't happen in 39.0.59.
Reproduce Steps:
1.Play any world or join any server.
2.Press ESC* in order to open Game Menu.
3.Click "Back to Game".**
Expected Behaviour:
Backing to Game.
Actual behaviour:
There's a fake "Saving World" and soon game crashes.
Launcher reports that
* If you Press ESC again Game Menu would disappear and you could continue to play it.
** If you click "Save and Quit to Title" it would successfully Save and Quit to Title