Not a bug bug, simply a consequence of the range being too low. But to my knowledge it is unique in that this is the only weapon that is completely unable to damage a boss. It's my belief that a player being able to softlock themselves should be considered a bug and should be fixed.

Some suggestions:

• Shard bomb rework that makes it a more viable weapon in other places as well as during this encounter. My preferred option but understandably unlikely.
• Increase radius of shard cores.
• Enable shards to spawn on the opposite end of low walls when close enough. Why should shard bombs be restricted from what swords, guns, and indeed other bombs are able to do?
• Replace thick borders on the side with thinner borders.
• Extend hurtboxes for the Roarmulii.
• Have shuttlebots frequently drop the airstrike damage item.
• Roarmulus rocket inflict damage in addition to the stun.