EDIT (Feb 18): We have released a new version (19.1.0) which fixes this issue. Please update your gamer!
UPDATE: The Special Skill has now been temporarily changed; the levels with Mad Hatter as the Boss should be safe to play (please restart the game!).
UPDATE: The Issue is caused by the Mad Hatter Boss Special Skill 'Mad as a Hatter', that steals beneficial status effects from the opponent. We are going to fix the issue with the Event Boss by temporarily changing the special skill of the Boss Mad Hatter to 'Piercing Strike'. This temporary fix will not affect the Hero Mad Hatter. The Special Skill 'Mad as a Hatter' is going to be fixed as soon as possible in a new build.
We are currently working hard on fixing an issue that causes the game to freeze when battling against Mad Hatter Boss. We will announce more information here as soon as we know more. Thank you for your patience and huge apologies for the inconvenience!