I do understand that the goldsmith is a very experienced person, who has worked with Gravograph engravers. However, without actually understand whether he is using the engraver the right way make it difficult for us to help him. As mentioned, he is unable to secure the ring properly on the jaws, thus this will make all the engraving uneven as the ring is loose.
I will get my engineer to do a short video on the proper way to secure the ring. Can you get him to view the video and from there on, we can better understand his issue?