I had the same thing multiple times. Ended up having to change the actuator, which solved the problem.
My mechanic never got to the point finding out whether a broken actuator made the gearbox throw error codes, or the gearbox itself was broken. There is no way to tell.
Would be interested in hearing from
@alfan his experiences!
Now, 20.000 kms later, I have a completely ruined transmission, with broken gear, broken actuator and broken TCU... So maybe it was the gearbox after all?
Car is at an official dealership as Alfa Romeo wants to consider intervening in the cost. Fingers crossed.
In the meantime, becoming crazy without my precious. Waiting for 2 months already...