Airwolf HD2x Z Adjust/Rod Endcap Replacement

I inherited(read "Found sitting unused in a corner of the storage room") an Airwolf 3D HD2x printer from work, and set about cleaning it up and making it useful. After replacing the hotend and updating the firmware, I started levelling the bed and noticed that I couldn't get it consistently level.

The Z height adjust knob is a clever little thing mounted on one of the Z guide rod endcaps, and is basically just an M3 bolt with a knob on the end of it that activates the Z endstop. But there's s