I got one of those bugs too and I thought it was because of the event but then I realized that it was taking more than what it said. But it's fine, I get the gist of it now.
I tend to use those coins to refill combativity, but for some weird reason the price stated to refill combativity and the amount taken differ. It's actually take more coins than it's supposed to.
For some reason, I'm not able to scroll down when choosing girls for the fights. It won't let me. Is that normal or is it just a problem on my end. Please let me know.