A simple test Look at the LED on the PMDX-126 on screw terminal connector J6, labeled "14". When you try to run the spindle one direction, that led will be either on or off, depending on your configuration (its late, I haven't looked at it). If you then try to run the spindle in the opposite direction, the LED should change. For example, if the LED is "on" when the spindle is commanded to move CW, then the LED should be "off" when the spindle is commanded to run CCW.
Are you seeing this? If not, you have a configuration error, hardware problem in the ESS or PMDX-126, or wiring error that is conflicting with the normal pin 14 functionality. If you ARE seeing the pin 14 LED change, then the problem is somewhere else (PMDX-107 configuration and/or wiring to VFD or VFD itself).