Sourcing parts from all over the place when you don't know much about them is almost guaranteed to get you in trouble.
I'd check the connections on the stepper modules, connections on the motors, and connections on the main controller board. Check for shorts with a DVM. Pull out the new parts and see if you can connect to the CPU. If so, plug in the new stuff one at a time and see which one creates trouble. That's not a guarantee that it's bad. It may simply not be adjusted properly. Once you know which part is the problem you can go on from here.
I'd check the connections on the stepper modules, connections on the motors, and connections on the main controller board. Check for shorts with a DVM. Pull out the new parts and see if you can connect to the CPU. If so, plug in the new stuff one at a time and see which one creates trouble. That's not a guarantee that it's bad. It may simply not be adjusted properly. Once you know which part is the problem you can go on from here.