Damage reduction items don't work first turn

I think there might be a bug with how damage reduction items work. When the player going first uses a tool like Metal Core Barrier or Steel Apron on their first turn, the player going second is able to do full damage on their first turn with no reduction. After the first turn, ongoing reductions like Steel Apron work as expected.

I have noticed this happen in several battles now, both as the player going first receiving incorrect damage and as the player going second dealing incorrect damage.