2 LPT port machine can only run one at a time stable

I put together another machine running Mach 3. This one is using the onboard parallel and a PCI parallel from CNC4PC. X & Y on one port and Z on the other (pins 2,3 for x step/dir, and 6,7 for Y. 2,3 for Z also). These go to an Anaheim Automation stepper driver. The AA driver has been used with another Mach system with no issues previously.
I can plug in either one of the parallel cables and control X & Y, or just Z smoothly. If I try connecting both cables, motion becomes erratic with missed steps.
What is going on?
I tried disabling the port instead of unplugging the cable and performance is still bad. This seems to mainly affect the axis controlled by pins 2,3. Whichever axis is controlled by 6,7 works fine with both connected. Pins are hardwired in the AA driver though so it is difficult to test different pinouts.
Need Help Please!
Thank you
Joe