Digital BW, The Print

I have a Pro 4000 printer that is having a number of problems. But right now I need help with one specific issue:

When I print the paper thickess page from "cutom paper" setup, none of the series of 2 lines are anywhere near congruent. The smallest gap is at line #1, and even here it is about 2 mm apart. Any idea what is up with this?

Thank you.

Shilesh