Sweep1: what´s wrong with the rail curve?

I know that in this case I have to be precise in picking the curves and did that.

The rail is build from a straight line and two tangent radii.
If the rail is fix loft and rebuild does not help.

Thanks @pascal how you found the blue curve?

´refit rail´ works but why it is not nice?

I work around in this case by split the red curve and build the front part with sweep2 (sweep1 also does not work). Other solution I can see is to ad a second rail curve at the other side of the green ones.

Andreas