Hey,
I tried removing the DYN4 driver from the equation, like you said.
I have connected a multimeter to XD+(poistive pin of multimeter)/XD-(negative pin).
In the Mach4 ESS plugin config, I set motor0 to CW/CCW, and tested the voltage.
When moving X-axis in positive direction I get 2.9V, and 3.5V in negative direction.
Then I tried to set motor0 to Step/Dir, in ESS plugin config, and tested the voltage again.
When moving X-axis in positive direction I get 3.5V, and -3.9V in negative direction.
I tested the Y-axis too, and it's the same.
TJoensen