Surface of an Alignment Incorrectly Offset on a Fence

Hello,
I am printing a fence with an alignment containing two elevation lines (Z1 and Z2).

There is elevation data for all of the alignment points for Z1, but I don't have elevation data for the first 10 points of Z2.
As I don't have elevation data I have left these 10 Z2 elevation points blank.

The problem is that when I print a fence, Z2 is shifted left. (i.e. it appears that point 11 (the first point on Z2) as been assigned the chainage of point 1. Z1 is printing correctly, and is not offset.

When I insert arbitrary number instead of blanks (say -999) it no longer offsets, however, I now have to delete the first part of the line to remove the artificial data I added.

Is there are large positive or negative number I can insert so that gINT treats it as a null value but wont offset the elevation points (similar to null values for surface grid points)?

I am using gINT Version 8.2.007 on Windows XP.

Thanks.

Calan.