Since I had to take the whole thing apart to replace the drive screw for the x-axis, I decided to replace the left-and-right side of the z-axis assembly with two parts I made on the CNC router.
The photo (above, left) shows the router mounted in the original mount. I had to raise the router in the mount so that the router bit did not extend past the dust brush (details on that later). That moved the router too far away from the table, so I had to jury-rig it to lower the whole router/mount assembly lower toward the table. The new sides to the Z-axis assembly (above, right) includes a "jog" to hold the router mount lower.
Here is the router mount. I designed it in cardboard, transferred the design to 1/4" hardboard. I verified the fit of all the components. I used a pattern bit on my router to duplicate the shape on two 3/4" pieces of plywood. I stacked and glued the plywood together.
The small hole to the upper right is for the vacuum attachment. It works fairly well, but I will re-make this with a 2 1/2" vacuum attachment. The more air you can move, the better.