QF72: How could a disconnected autopilot change the pitch?
The A330 has a degree of automation that can't be turned off, as part of its 'fly by wire' system. 

This is to say that the pilot's controls aren't directly connected to the control surfaces. They are electronic in nature, sending signals to a controller which then decides how much to move the control surfaces. 

As part of that, an automatic feature is built in to prevent the aircraft from entering flight attitudes that could be dangerous. This safeguard detects unsafe flying conditions using input from the the Air Data Inertial Reference Unit (ADIRU). 

In the QF 72 case, a fault in the #1 ADIRU led it to believe that the aircraft was in a 50 degree nose up attitude, so it automatically forced the nose down. Problem was... the aircraft was flying straight and level, so the result was a very sharp nose down attitude, with negative G's applied to to the cabin (and everyone in it). Anyone not strapped in was slammed into the ceiling, and then into the floor when QF72 recovered from the dive. (only to do it again) 

In this case, it wasn't a faulty AOA sensor, but a faulty ADIRU, which appears to have hit an unforeseen combination of inputs... and an unfortunate combination of data and timing that led the Flight Control Primary Computer that actually runs the control surfaces to not figure out that ADIRU 1 was giving it faulty data. 

A couple of months later, QF71 encountered the same problem. Fortunately, the pilot was familiar with the QF72 incident, and simply switched the FCPC from the faulty ADIRU 1 to the backup ADIRU 2 that wasn't experiencing a problem. The flight continued without incident. 

So the issue wasn't really a faulty AOA sensor, it was faulty code in both the ADIRU and FCPC, which appear to have been triggered by a rare combination of ordinary circumstances. 

Note that a frozen angle of attack sensor and consequent incorrect automation responses led to the crash of XL 888, on an acceptance flight when the A320 was due to be returned to Air New Zealand after a lease.