3d slope to target from 3d geometry tools don´t follow target

Hi

I have existing terrain and future terrain, where I create 3d slope from FG terrain to EG terrain. The slope don´t follow the target terrain and goes below along one side. Because of that i get a CUT from the volume analyse where there shouldn't be none.

I am using PowerCivil 3d SS3 for Denmark

Regards

Sigfús