So far, after about 250 break-in rounds (FTF 3 times in the first 25 rounds. After that it has run perfectly.
While reading about the PM40 on Kahr's website I also looked at their accessories, namely fiber optic sights. Kahr notes both their old slides and new slides. The new slides have a very small dimple on the underside that can be seen when the slide is locked back. I bought the one with the dimple thinking that if there were old problems, the newer models would have the benefit of the up-grades.
So far so good, look for the dimple.