Focus blending "staircase" artifacts

I've been experimenting with Focus Blending in ON1 RAW 2020.1

I have 10 images which were captured using Olympus auto Focus Stack which I'm introducing into ON1 using the "Focus" button and letting the program do it's thing automatically.
The results look OK, but close examinatlion reveals some "staircase" - like artifacts in one area, which I don't seem to be able to get rid of. Adjusting the "Sensitivity" slider improves things slightly, but I still have a staircase like edge on the left.
I'm attaching two crops of the offending area, the alternative, smooth version was created in another focus stacking program.

Focus Blend using ON1

Focus Stack using "Affinity Photo"