The bug
When the game is closed and then reopened within a few seconds, an error message appears:
It says “This game is already running. If you just quit the game, it should be ready to launch again in a moment.” Clicking on the link takes you to a page that recommends you reinstall the game.
This did not happen in previous versions.
How to reproduce
Close the game
Open the game
Expected behavior
The game should open
Observed behavior
Error message
This occurs because the Minecraft process does not immediately exit after the game is closed and continues running in the background. During this time, game audio can still be heard.
How long the process continues running depends on how much RAM the game is using. The more RAM that is in use, the longer it takes for the process to exit, which explains why the issue does not always occur. If you observe the Minecraft process in Task Manager, you can see that its memory usage gradually decreases until the process finally exits.
Because of this, "The Minecraft process does not immediately exit after closing the game" would be a more accurate title and description of the issue.