We had confirmed an issue that select dungeons did not have the special 0 Stamina Cost bonus applied to them.
See here for details on the special 0 Stamina Cost event: https://bit.ly/2KRbfc1
This issue has been resolved as of 5/1 (Fri), 4:53 PM (UTC-8).
Magic Stones will be distributed as compensation to players who entered the affected dungeon(s) between 5/1 (Fri), 12:00 AM - 4:53 PM (UTC-8).
The compensation will be delivered via in-game mail starting on 5/12 (Tue), 7:00 PM (UTC-8). Please allow a few minutes for the compensation to be delivered. If you do not see the compensation even if you have entered the affected dungeons during the times listed above, please restart your game.
We sincerely apologize for any confusion this may have caused and thank you for enjoying Puzzle & Dragons.