UPDATE 2024-08-27 12:25 UTC: 

Thank you for your patience! Following the conclusion of the Secrets of the Opera Challenge Event, we have thoroughly examined our logs and accurately determined how many Challenge Coins each player would have earned from Suspicious Chest enemies had this issue not been present.

All affected players have now been sent the correct number of coins—plus a little extra—as a token of our apology for the inconvenience. Please note that it may take a little while for our message to arrive at your in-game Inbox.

Thank you once again for your patience and understanding!

2024-08-22, 13:10 UTC: We are aware of an issue that causes "Suspicious Chest" Special Enemies to not appear in the Secrets of the Opera Challenge Event stages.

As making a sudden mid-event change would be unfair to many players, we have decided to fix the issue AFTER the ongoing event ends. This means that Suspicious Chests will not appear at all during this event. Please refrain from replaying the Secrets of the Opera Challenge Event stages to find Suspicious Chests.

We sincerely apologize for the inconvenience. We will review the situation after the event concludes. Thank you for your patience and understanding!