Unsure if this is intentional, but the 1 damage you take from playing Bungled Bolt will not cause Shimmer Aura to trigger, even though the source of the damage is magical.
Shimmering Aura only prevents Magic and Projectile damage. Those are attack types. Bungled Bolt causes 1 point of Arcane damage. Arcane is a damage type, not an attack type, therefore Shimmering Aura doesn't protect against it.
