
He called me and I went over to his place of business to inspect the defective part. I noticed that the stem bore had what appeared to be one or two drops of smeared and cured epoxy on the bore wall. I confirmed it was epoxy and not dop wax when I heated a piece of it.

You can see the small amount of epoxy by looking on the bottom of the faceting dop holder. Note that the wall of this bore appears relatively smooth.

There are four issues I see here:
1. Unnecessary helical pattern in the insertion end of the stem.
2. Smooth surface finish of the stem.
3. Smooth surface finish of the bore.
4. Insufficient amount of epoxy to secure the stem in the dop holder.
I have had to correct many issues with this machine, so rather than act as unpaid quality control and send it back, I repaired it myself by lightly sanding the surfaces to be mated with 180 grit silicon carbide sand paper and rinsing them with acetone. I then applied JB Weld to those surfaces, mated the parts together, oriented the stem and let the epoxy cure.