Also your rail curve produces a surface with very bad tangency where it connects to the 15mm rad fillet.
To get good tangency on the ends:
find the centerline of both blue fillets
then use Blend Curve between the 2 centerlines and
then pull that curve to the vertical 20mm fillet.
If you use history on steps 2 and 3 you can edit the blend curve by using Scale command on the second from end CV and using the end CV as the origin point for the Scale.