[2020] Twice in my most recent battle, I used a Special Ability while slots were available and no Vulture Droid was summoned

Were there available slots to summon an additional Vulture Droid? (You only can have 5 ships on the field/in the battle at any given moment). Additionally, only "Charging Malevolence", "All Cannons Fire!", and "Fire the Ion Cannon!" are special abilities.