Dave Hoffman correct, the tabs turn with the tube. You have to get a nice grip on the tube and turn hard.
Same problem here. In order to rotate the tube to the unlocked position, the tabs would need to be shaped like a "ramp". They are however square in shape and I can see no way to force the tabs back out of the slots.
I did think of one way though - you will need 6 men - one to hold the motor unit, 4 with flat screwdrivers one to pry at each slot, and one to twist the tube.