I think it is pretty common to find the timing out before the belt has been changed.
A combination of not using the correct tools when it was last done, and some belt stretch will mean it is out slightly.
I have done 5 x TS belts and 4 of them had incorrect timing to start with..
Just because it was done before by an Alfa dealer of specialist doesn't automatically mean the correct locks have been used. The attitude "I know lots about these engines, I can do them without the locks" does seem to surface from time to time.
Giulietta 2.0JTDm (170), BMW 335i Cabrio, BMW 120d