Regarding Arena Duels in version 1.1.0 (Notification)
Here's some info about Arena Duels in update ver 1.1.0:
If you participate in Arena Duels and close the Fire Emblem Heroes application mid-battle, then later resume the battle again via bookmark data, you may not get an extra score boost while using Bonus Heroes.
Your Arena Defense Reward score may be displayed inaccurately or not appear at all. Note: You will still receive the correct reward.
We are now investigating this matter.