unequal segments after pattern along an ellipse

Hi,

I have a problem with pattern along a curve. I have a point on an ellipse and I do a pattern geometry with constant pitch of 20 mm arc length along this ellipse:

Then I use a divide curve command and divide it with my patterned points:

I don't understand why the segments of my ellipse have not the same exact length of 20mm?!?

When the path is a line or circle it works OK. But it gives me unequal length segments with conics, ellipse and even spline.

Also I checked the other methods rigid and offset. The problem still exists.

Anybody has any Idea?

Thanks.