OK, very strange behavior is happening now, see below. But first to address the questions:
Hood - yes I'm using a licensed copy of Mach.
Gerry - thanks for the info about the safe Z retract. I will add that back to the macro when I have figured out why it's not behaving properly after touching the plate. For now I would be happy to get correct and consistent results from this macro.
Tweakie - I added your line "DoOemButton(1003)" where you specified. This caused some very strange behavior. What does this do?
1. The direction of movement was frequently up instead of down when doing the probe move. But it wasn't consistently wrong. This seems to be before it even executed your new line.
2. When your line was in the macro, after touching the plate, the machine moved on the X and Z axes simultaneously when it tried to retract. It moved about 2 inches to the right as well as moving up about the 0.25 inches specified by the macro.
I am quite mystified by this, so if anyone can set me straight I would appreciate it very much.
Thanks to everyone.
Greg