So to reproduce this, I have no clue, but it happens every time I go to play. I load the Minecraft launcher and when I press play on any version of Minecraft, the actual game only closes when I manually close the two processes for the Minecraft launcher in task manager.

So for me it's as follows:

     1. Load the launcher up.

     2. Select any version of Minecraft, whether it's modded, vanilla, or on a fresh install of the      game.

     3. Press play.

     4. Wait for the MOJANG screen to pop up and the launcher to visibly close.

     5. Navigate to task manager.

     6. Close the BOTTOM of the two tasks known as "Minecraft Launcher (32bit)" located underneath the background processes tab.

     7. Wait for them to close out one by one.

     8. Wait for Minecraft to stop being unresponsive.

     9. Enjoy the game you guys worked so very hard on.

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