Axis will jog slowly to get off a limit switch (if you are in a axis limit state). Swing the control away from the head (it is on hinges), and remove the plate behind it allowing access to the Z switches. Make sure a wire is not loose or caught there.
In the back of the machine, there is a long terminal strip. You can go along it and check where the 24 VDC stops to see which switch or wire if giving you grief. Check the wiring diagram for relevant wire numbers.
The switches have a rubber diaphram between the plunger and the switch itself. These fail allowing coolant inside the switches (table and saddle). Make sure these are dry inside and no wires have rotted off. Yes, I have seen it many times.
George
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)