FiveGirlKit
The left thrust lever has operated correctly; the problem is that in response to a thrust reduction command, when the climb mode of FLCH/VNAV - THR; changing to ALT CAP -SPD, that gives a thrust reduction. In the first instance, the left thrust lever comes back slightly, as the AT tries to maintain the commanded speed, which will probably be 250KCAS. As the RT TL is not being picked up by the clutch, the AT will increase the thrust reduction command, and effectively close the LH TL to idle or near that.
At 35 bank the GPWS Mode 6 "BANK ANGLE " sounds continuously. If the bank angle of 45 is correct, then sometime thereafter the APLT has disconnected, which can be determined how, and the aileron that has been applied has to be taken over by the pilot, which is probably not the case. Disconnect with a large aileron deflection often ends up with inadequate force to maintain the existing displacement and a return to a near-neutral aileron is highly likely. At that point, the roll rate is going to accelerate away from desired bank due to the yaw that still remains. The roll rate from the yaw is around 25/s so the aircraft is at 90 bank in a couple of seconds, and what the crew then do is going to be a major factor. the roll to the right is compromised by the more than 90-degree deflection needed on the yoke, but of all of the potential upsets, a captain in the left seat is going to get more right aileron on than the FO, If they are using their outboard hand only. If they grab the controls by both hands, then they have a reduced likelihood of getting full aileron on. With a bank of 90, more RH aileron is required as the natural tendency is then for the nose to fall and that increases the yaw and the subsequent roll rate, so it is not surprising that the crew get confused. (1994 Buff bingle Fairchild, "Budd" Holland and his unfortunate crew.... 2010 Elmendorf C-17 is slightly different, but kind of close) Approaching this point, the nose is going to start slicing down, and speed is going to start to increase, but so will the g loading, so initially the speed will not build rapidly. if the aircraft stalls (not necessary to have this event) the aircraft will rapidly roll inverted, and the nose will drop towards vertical promptly. Speed will increase rapidly but the plane steeply noses down, possibly still with the asymmetry complicating the recovery. Without a stall, speed/aoa stability will assure that the aircraft at the 90 bank or steeper will start loading up, and as soon as the vector is below horizontal, the g will build up rapidly, and the aircraft is going to have a steep spiral, It is possible the crew follow through with the roll at that point, it wouldn't be the first occasion of a crew doing that (B717 stall wild ride) It is conceivable that the aircraft recorder ends with the TLs still split, LH at idle, RH at climb thrust. There are surprisingly few ways to get from A to B in the time available; from the first report, a roll excursion was likely. reminiscent of Sharm Al Sheik.