Refer to: Is ammunition recoverable and reusable?
You can't recover a single valuable magic arrow fired into battle due to the general rule of rounding down applying to the weapon property that lets you recover half of the ammunition that you used at the end of battle.
This interaction is frustrating since the weapon property clearly indicates that you are supposed to be able to recover half of your ammunition. Losing out on valuable loot is not fun. So it seems sensible to fix this odd rules interaction with the simple houserule that you omit the rounding down rule in this scenario.
Are there any weird rules interactions such as a magic artifact that always lets you recover one arrow in addition to half of the ammunition that you used at the end of battle that would result in enabling players to recover more arrows than they used or similar interactions that would create further complications when I houserule that the rounding down rule doesn't apply to this particular scenario?