The "castings" as they have been referred to in revious posts are more than likely parts machined from billet in -0 state, after machining they are then heat treated in an oven at set temps and times to achieve for example T3 or T6. Most machined parts like the ones in this topic are generally treated to T6.
The material in T6 state is usually to hard to obtain a smooth surface after machining and thus stress risers are induced during production process.
It is a possibility that damage has occured to the involved parts due to incorrect removal/fitting of the actuator where one or more gouges occured on the part(s) involved. If such gouges are/were present they will result in fracture.
To my knowledge the big Airbuses use the spoilers to effect roll at high(cruise) speed (combined with inboard aileron). Outboard ailerons were present deflect only at slow speeds.