After exiting the Unable to Verify Game Ownership message, holding down on the mouse and trying to move it will lock your mouse until you let it go. To stop it go to the menu and back.

Steps:

1. Get the Unable to Verify Game Ownership Message in a game.
2. Close it by pressing Continue.
3. Hold left click and try and move around

Expected Result:

I should be able to move around my move when holding left click.

Build: 1.8.8.0_5887792

Notes:

This happens every time, after rebooting, restarting Minecraft Dungeons and reinstalling it.
(Also to clarify I already bought Minecraft Dungeons and there is a separate issue about the message appearing)