Bezier curve takes multiple frames to resolve

[_Aka_]

alright... I have found a solution for now... after setting the control point's position and rotation, I SetDirtyAll(), then Refresh(), then make my changes to the bezier handles and it appears that the curve looks right at that point.
 

Yes, that's what I meant when I said "So basd on this guess, try refreshing the spline after each modification of the spline. It's overkill, but it might pinpoint what exactly goes wrong."

About the remaining of your last post, I agree with you. It is something I wanted to work on since I acquired Curvy from its previous owner, and I finally started working on it three weeks ago as part of the next update.