Ice Bucket Coupling & Auger Motor Drive Shaft BOTH. I ordered both parts but at first only put in the Ice Bucket Coupling piece as this was the easiest and quickest part. I purposely wanted to do only this part first to see if it completely fixed the problem. Well, after replacing only this piece it was stronger and when I would hold the ice bucket arm (it's shaped like and upside-down question mark and you have to press the door trigger and have someone push the "ICE" trigger on the outside of the door) --- when I would trigger it on and hold the ice bucket arm to simulate a bucket full of ice it WAS stronger but would still slip a bit under a load. I replaced the Auger Motor Drive Shaft next and after doing so the ice bucket arm was much much stronger.
Personally I recommend that if you have a stripped ice bucket coupling and/or Auger Motor Drive Shaft, replace BOTH of them, as if one is stripped, the other part is not far behind.
Also, take the chance to clean all the mold... see my photos, as this was from the previous home owner, however I'm certain there's literally NO ONE that looks at this OR cleans it, ever. However if you're wonder how you may get strep throat... well here you go, bacteria in places you'd likely never look:
https://photos.app.goo.gl/WiCfLfvpiKZ9N3QG2