Angle command refuses dupe edge line even when proj Cplane...why?

I have a simple sweep 2 rail, its in another post in fact, I dupe edge its bottom edge, project that to Cplane
draw a horizontal line, select the dupe edge one then the horiz and angle says now select second line !!!

I attach that file here…try it, dupe edge the bottom slightly sloping edge in Front view, proj to Cplane, drag it down a bit to see it, draw another horiz line, angle command refuses it.

It should be 1.33 deg

Skin sweep A capture of crease.3dm (120.2 KB)


Works fine for me, both using Angle with the TwoObjects option and by selecting points on the lines.