I've now tested your driver. I connected it up in place of my Y-axis driver. I use *752 series drivers, so they're on 70 volts hence I used a lab PSU set to 48V for your driver. It works fine... I've not done anything to it, just connected it and changed the switches to 1600 step/rev as that's what I use. Then tested it on 800 and 400, not really expecting that to make a difference, and it didn't.

Interestingly the motor runs more quietly and possibly more smoothly (difficult to tell of course) with your driver. I'll have to test my own driver on 48V to see if it's just the lower voltage causing that. If not then that's useful information as it implies they use different control algorithms. As expected though the feedrate I can get with 48V is less (24000mm/min @ 2000mm/s/s acceleration) but still plenty!

So what would you like me to do now? Just send it back and hope it starts working on yours too? I'll have a look inside anyway just to be sure.