If you equip an armor with multiple cooldown reduction and bow with Infinite arrow (chance to not use ammo), you can shoot firework arrow multiple time and reload with fast with short cooldown. If you carry 2 x Fireowork arrow and spam those back to back, 1 or both firwork arrows sometimes get greyed out and you cannot use any longer. Happend to me about 5 times now. Everytime you can fix by unequipping the grayed out item and requipping it. Horrible bug.