Hi FT
I had a similar problem a couple of years ago. After a long saga and much (free) help from Redline, it turned out to be the quill. Believe it or not, it makes a difference depending on whether you put the quill into the box and then attach the angle drive, as opposed to putting the quill into the angle drive and then attaching the lot to the box.
At this time of night I can't remember which was the right way, but if you are still having trouble, blat mail me and I will try to find the post of other record
Terry