offset surface node does not work with loft tool

Hi

in the following example you see an array of points through which a poly line is drawn.
a loft command skins the three curves and an offset should create a surface.

however this only works when the 3 loft curves are the same.
the moment one point is being moved the offset surface fails.

this doesn't make sense to me. what could be a reason for that.
working

failed:

you can also see that the curve offset produces not problems but than the loft
command does not show any surface but also does not give any visible surface.

claas