reproduce the bug: click on Reio Guardian event > click on Guardian Mythology > after spending all free daily chances > click on Start Janken > click on either rock, scissor or paper => => there a window pop up with thext:
"Janken chances used up, spend 50 gold or coupons to continue?" > click confirm > it just says: not enough gold; it does not consume coupons as stated (sort of misleading)
