Gsender not working with openbuilds blackbox

I have installed the latest version of Gsender and I would like to use it with my DIY cnc router that is using an Open Builds Blackbox as the controller. I have been using the cnc for the last 5 years with the Openbuilds control software and everything works fine. I am changing software because I have a Longmill as well and I would like to be consistant with the software being used.

My problem is in Gsender, I am able to jog the x and y axis in both continuous and incremental modes. but I am only able to jog the z axis in incremental mode. Does anyone have any suggestions on what I may need to do to get this to work?