I don't think they're from parted out 0S. See the black O-ring at the end of the bicep? That wasn't present on the previous VF's, I think they're to reinforce the swiwel joint.
The stress marks are also different. They were like thin hairlines before, now they are wider and fuzzy. It shows that:
1. The shoulder housing is too tight.
2. The balljoint is too big.
3. The workers at the assembly process are screwing the shoulder halves together first, and then popping in the shoulder thus causing the stress marks.
The shattered bicep is inexcusable though
Once when I was transforming my VF-0S from fighter to gerwalk, the forearm popped out from the bicep when I pulled the arms out.
DISCAIMER: I'm not saying that odr78 used too much force, but the added screw in the ultra thin bicep weakens the whole area.
I'm very lucky with my two Zeros. The VF-0S has no stress marks and the VF-0A CF has a tiny hairline crack in the left shoulder.