The Add Turret target has been used incorrectly.
In the layout, for the ArrowTower, Disable the Initial state of the Turret behaviour. In event 8 (placement) add ArrowTower->Set Turret enabled. From event 19, copy the Add Turret target action and paste it to event 1 (On start of layout). Disable/remove event 19.
It's a subtle point, but the manual does mention that the Add Turret target need only be called once per object.