Brep rotates by flowing

for generell understanding, what i’m working at is to bend a twisted timber-board to multiple radians in generally two directions (always around its ‘weak’ axis).
the problem i have is, that the twisted brep (twisted timber-board) rotates in a way i can not influence when i am flowing it by the targetline. so as you can see the brep is then bended around its ‘strong’ axis.

does anybody have an idea how to control the flowing-process or how i can change my targetline so that this rotation does not happen?

see attached file. i can even give you the generating file in detail.

thanks, j.brep rotates by (13.0 KB)