Help with a 9" SB

[upnort16]

Greetings to all and I am seeking advice on a southbend 9" model A lathe I recently purchased. I have a 10k as well and here is the problem. The 10k cuts screw threads with absolutely no problems, but the 9 does not. I seem to get a new cut on every pass, meaning the tool does not seem to hit the same mark twice. Now I am no machinist, but following the southbend pamphlet and duplicating exactly what I do on the 10k does not work. My thought is I am not getting the half nuts engaged properly, but even taking great care does not yield good results. Is there possibly a concern in the apron, perhaps the star wheel clutch as it does not fully disengage at times. This lathe was completely overhauled. Bed scraped and the whole shebang, but not by me. Everything is tight, including engagement of half nuts. Not worn in like the 10k, very crisp with little backlash throughout. What should I look for and any and all help is appreciated.