Do you still have the logfile for the night in question? If so can you post it? It’s hard to point to a problem without any data to look at.
Did you notice at all what quality level your AF runs achieved? It should be in the log file or an AF pack if you saved these. My first thought is that despite ‘looking good’ the quality score achieved was below the required target level, thus triggering a re-run.
With regard to step-size, did you take a look at the number of focuser steps needed to go from smallest HFR to c 3x this value (x1.5 if looking at HFD), see AF set-up notes.
I had a similar problem with my SV115. It turned out that I had not tightened my Crayford focuser in a few years and it was slipping with the heavy camera (QSI-683). After tightening my focuser, the AF worked fine. Of course, if you have the rack and pinion focuser, this is not likely to help.
so here is the strange thing. I went thru the calculation and got a step size of 173, 2x2 binnng. I worked perfect after I did that (ran it 15 times). I did not adjust the backlash as stayed at 40. The next night with great skies I went to same location 19,740 ran auto and no V curve and could not get auto focus to work. when I went back to same location, stars were out of focus at same location. I am using an optec directlyncs focser . Beyound fustration. Totally frustrrated. Any help would be greatly appreciated.