Does anyone use Geckodrive G-Rex G100 with Mach 3 (2010 screenset or regular) and have a WORKING auto tool zero macro?

My touch plate probe is set up on pin 15.

Here's the 889 macro...
Message( "Auto Zeroing..." )
If IsSuchSignal (22) Then
code "G31 Z-3 F20" // Moves probe down 3 inches
While IsMoving()
Wend
Call SetDRO( 2, 0.625 ) // sets z to zero assuming plate thickness is 0.625"
code "G1 Z1.0" // Retracts Z 1 inch.
End If


Problem is.... this macro works perfectly only ONCE. Second time it retracts way more than 1 inch and eventually hits the limit switch on the Z axis.

Any ideas what could be wrong? Or should we conclude that Grex G100 auto tool zero macro will never work with mach3?