In the scene I sent to support, I have no abilities other than Equip Verifier, the only item abilities are use slot 0, use slot 2, and equip unequip, and the only items are the body item and the other item which is an empty with a melee action.
Additionally, went into the demo scene and changed the shield to a melee weapon, and equipped both sword (slot0) and shield (slot1). The same behavior I described is observed when I use the melee shield while the sword is swinging: the sword (slot0) trigger is set when the shield (slot1) is used. Using the shield (slot1) is not mapped to aim so that is not triggering slot0.