When I use the PullCurve component (from Curve → Util) it misses some lines of the original polyline:
But when I explode the polyline into lines, it works correctly:
Isn’t that a bug? I mean - the lines of the polyline are the same - with or without exploding.
See attached GH file - use value list (dropdown) to switch between polyline and lines. There is also a panel showing the reduced number of lines after pulling - when polyline is used.
pullcurve_bug.gh (15.1 KB)
don’t know exactly why, but looks like extending your pulling surface solves the problem
(probably extending it just toward the bottom by a few units could already be enough to contain those missing segments that would go lost in the pulling?)
Thank you very much for spending your time on this issue and proposing a work-around. I highly appreciate your help, but honestly speaking I was not searching for a work-around, because I already have the one using exploded polyline into lines, which works perfectly.
I wanted to point out that there is bug in the pullcurve component to let someone at McNeel look into it and correct th pullcurve component to make it more stable and reliable.
But I have no idea whom I should address this to. Do you know?
@DavidRutten I think the above mentioned issue with PullCurve component is clearly a bug.
Since Pullcure is quite an essential component I would suggest to put that into the issue tracker and fix it in a future version.
I had chance to make a few experiments, and found out that if you bake the curves and the surface, and try to use the Rhino command “Pull” on them, it also outputs the very same trimmed curves as in the GH definition:
but if in Rhino you activate the option “Loose” then the result looks “complete”:
at the same time, decreasing (A LOT) the Tolerance in Rhino Options, improves the amount of polyline that GH is able to compute
there’s for sure something weird going on with Pull Curve, or maybe there’s some important background explanation about how the command works in detail that we are not aware of 
