I can't unroll the surface created with D-Loft

Have you ever came across with the surface that is enable to unroll? How do you fix it?
File attachedtake 5 - rails.3dm (718.9 KB)

Your surfaces will unroll if the narrow tips are split off and unrolled separately…

Many thanks @davidcockey for the explanation. D.LOFT tries to handle this problem by moving the final control points a tiny bit from their common tip, but that seems not to be sufficient in this case.