It is not easy to spot the difference in so small a picture, but the surface of the abnormal arm seems to have more gloss. Is that correct?
Is there any tolerance for surface roughness or gloss level?
Does the surface in question have any practical function (other than holding the part together)?
Did you observe any difference in surface gloss on the raw material (i.e: did it appear during your operations or earlier in the process)?
/Claes