Winemaker
The suggestion was made that it’s possible for the auto thrust clutch to fail, and that could lead to the power of one engine to reduce, possibly all the way back to idle. I’m not on plan B, so not sure if they are suggesting the throttle itself would move too, but I would guess it would. Having one engine at idle, and the other at climb thrust would obviously induce a yaw. If this would happen with the autopilot on, the autopilot would try to maintain the path with ailerons deflection, but it has no automatic rudder trim, so the aircraft would have a sideslip. I would think that as long as they were climbing in an airspeed mode the speed would not have gotten low enough to get near to any Vmc condition. It is possible that, perhaps because of the loss of performance the pilots selected a higher climb rate using vertical speed, and the speed loss that followed lead to an autopilot disconnect and loss of control because of the out of trim situation, but that is pure speculation.