interpolating points to make polylines

Hi to all,

I have an issue trying to make polylines off of points evaluated on a set of curves. I thought it was a simple fix but haven't been able to make it work. I have no duplicate data nor other weird issues prior to this point. Any insight would be of much help! Let me know if you need files.

I have 28 curves:

The curves get evaluated with variation from graph mapper:

Then the matrix needs to be flipped to generate curves in the other direction, but linking order distorts:

The polyline seems to jump to point on a different parameter, gradually affecting overall linkage:

Happens at top or bottom if I reverse the inputs:

Still happens when polylines are derived individually: