This is the Happy Wars Management team.
From 9am UTC on December 9th until 2:30am UTC on December 12th, there was an issue with the Xbox One and Xbox 360 cross-platform Co-op mode.
Details:
In Co-op mode’s normal difficulty, if you got the “Superb contribution!” achievement, the boss-killing reward was selected based on incorrect chances.
The issue has been fixed.
As an apology, all users who have played Happy Wars before December 12, 2016 will receive 6 Happy Tickets. You can receive these until December 30th, 2016
We apologize to all of our users for any trouble this caused.
About the boss-killing reward Issue