Sorry, I don't have enough experience in Walls. Heck, I don't have enough in the one I use either other than to guess randomly until I get it right.
This document doesn't get into much detail
http://www.cavediggers.com/walls32.pdf, but it has some things they've done. I'm curious whether there is an issues with the #segment that you are in, with the way you're entering GPS, or something else.
Best of luck.