David,
I don't know your level of expertise with CNC routers, but the 'Go to Zero' button on the Mach 3 main screen is NOT used for sending your X, Y, and Z axes to the "Home" position. That button sends your axes to any one of the six Work Offsets (G54 -G59) you set up and select on the Offset screen. Mach 3 defaults to the G54 offset. So what ever value you have in the G54 Work Offset screen is where Mach 3 will send the router when you hit the Go to Zero button. Remember, the G54 offset value is ALWAYS referenced (measured) from the Machine Zero (Home position).
The Go to Zero button will also send your router to any location you set up for "Part Zero" (X=0, Y=0, Z=0) on your work piece (wood). Part Zero is usually located at the lower left-hand corner of your work piece. Once you move your three axes to that corner and "zero out" the X, Y, and Z DROs (Digital Read Out) in Mach 3, the Go to Home button will go to that position automatically every time you hit that button - as long as you start at the HOME position.
Ok, so don't use the Go to Zero button for Homing.
(Sorry for being so long winded)
Now, it's the G28 X0 Y0 Z0 G-code command that will send any CNC router to the Home position. Most G-code programs will have the G28 command at some point in the program to raise the Z-Axis first, then the X and Y axes.
You can see this in action by going to the MDI screen and typing the following:
(Make sure all fixtures and clamps are out of the way.)
G28 X0 Y0 Z0 (Rapid movement)
or
G28 Z0 (hit Enter)
G28 X0 (hit Enter)
G28 Y0 (hit Enter)
If you get a hand held "Pendant", you can set it up (OEM codes) so when you hit the Home button on the pendant it will automatically send your router to the Home position. The OEM codes also work in "Script" files.
Let's get back to your problem. Here are a few suggestions:
1. Go to the Config tab on the menu bar and select 'Homing/Limits' from the list. You should have all green check marks under the heading 'Auto Zero' column. Also, play with the Speed percent setting. It may be too slow/fast.
2. Go to the Config tab on the menu bar and select 'Safe Z setup'. You should have a check mark next to 'Allow Safe Z moves'.
3.If you have the 'Soft Limits' button turned on (green) on the main screen in Mach 3, go to the Config tab on the menu bar and select 'Homing/Limits' from the list. Make sure you are not out of bounds with your settings.
4. Go to the Config tab on the menu bar and select 'Motor Tuning'. Your Velocity and Acceleration may need to be adjusted (motors too slow or too fast). They may be struggling to keep up.
Hope something I suggested helps,
Roger