Centreline makes my form distorted

[Anonymous]

Hi, this is my first post!

So, I'm following the product design tutorial on the academy and I guess the video is for a different version of fusion. Anyways, if you look at the three screenshots you'll see that once I add the centreline for the loft form, the shape becomes distorted instead of a smooth curved shape. Any help would be much appreciated, thanks in advance. 

[TrippyLighting]

These dots I have circled in red rare the twist control handles. If you pull around on then you can untwist your loft.