I also have a 1C but have never used the auotfocus so I can't help with problem. I have also the V35 and even with that you can't rely on the autofocus that much, so I just view it as a help with sizing and that's all.
With the 1C and V35 I always check the focus with a magnifier before doing each and every print, so the aotofocus accuracy is irrelevant to me. I ave found this with all the autofocus enlargers that I used, not just Leica.