Blend problem

[gnurf]

Either I have a mental block or it might be a bug (or something else)

I try to make a blend like in the attached image for a perspective image but I only seem to get a "straight" blend or a "twisted" one. I've done similar images in previous versions of Xara and haven't had the problem before (as far as I remember which isn't always that far ), but now I don't seem to get it to work no matter what I do (I tried flipping the ellipse and converting to shape etc)