Bottom chamfer on print has inconsistent quality

Hopefully someone out there knows more than I do.

The bottom of my model has a normal 45 degree chamfer for several mm. I have been trying to find ways to adjust settings to get the model to print faster. The results are fine at slow speeds. At a certain point, I start getting strange artifacts and visible layer separation, that in some cases starts looking like the bottom of a bridge.

I am using default line widths, so with a 45 degree overhang, I would expect the outer wall to have a .2mm overlap. 2mm up and .2mm out.

I have been fiddling with slicer settings and looking at the previews to see what might be happening. This is the flat bottom with one outer wall in yellow (viewing from the bottom).
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No surprise. Now I add a few more layers and what surprises me is that I can see inner walls between the outer walls on the chamfer.
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Is this just an artifact of the way the slicer previews, or is there really space there?
Reducing elephant foot compensation did reduce the inner wall show through for the first layer.

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In this view it looks like it just stops printing the outer wall.

If I change the outer wall width to .6mm the inner wall show through between the chamfer layers goes away. However, the gap where two chamfers meet is just the inner walls.
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I would appreciate a discussion about this to share the knowledge.