I just had a really bad failure with the A330-300 cruising at FL370 from KMIA to EIDW.
Over the North Atlantic, I encountered one of those crazy wind shifts. The aircraft hit MACH .99 for a second and bounced back to normal, but the autopilot did not like that and disconnected.
After that, none of the management modes worked. I could not follow the navigation track, the heading bug vanished, and the altitude would not hold no matter what I tried.
AT would not control the throttles in any mode.
The performance page was in DES. I could not go back to cruise because that would activate the Approach phase.
Sadly, I had to cancel the flight.
Luckily I havent encountered anything like this with the A350 but this is no bueno for long haul flights in the A330.