It falls into the "nuthin's ever easy" category. First I found the 355 "driver cup" had split - - comments on your website often stated that replacing the cup often didn't last long. Upon taking it apart, I found that the 356 "Plate helix lock" rotated on the shaft because the "double D" flats on the part had worn round. I ordered it and the 357 "helix" just case I broke it while removing the Plate helix lock. As it turns out it just falls out. While attempting to remove the 320 "Auger Nut" I found it had screwed itself further on the shaft and wouldn't just unscrew (yes I viewed you video and found it was a left hand thread - - thank you) because it was driven too far down the shaft, I had to pull it to the point where it would unscrew (I should have purchased one of these also if I had only known) - - it did screw back on and seemed fairly snug - - we'll see.....
I assume that other references to the drive cup failing prematurely was due to the 356 "Plate Helix Lock" also failing.
So far it is working "just like new".
Thanks very much for your videos and prompt parts delivery - - you folks are great to work with:-)