Mactec54
You have a poor ground on the signal side of the driver. Shielding the power side is not necessary, just don't run signal cables beside power (or motor) cables. Ground all signal cable shields from one end only, never both ends. Use a totally separate signal ground. Do not tie it to motor shield or earth grounds - doing so will cause a ground loop. Use a star configuration for signal grounds (returns). Earth ground is fine for cabinets and motor shields, not for signals. That is run as an earth bond to major mechanical structures but not signals. The purpose of the shields is to eliminate induced EMI not to provide grounds. A ground block is fine for signal grounds and returns. Grounding everything together is very bad practice. The reason you are having problems is that the ground threshold at your amplifier is bouncing causing false triggering of your inputs. If you have a scope you can check it out. If not try adding a ground from your power supply negative directly to the signal ground on your driver module. Cut the shield loose on one end of every cable. I worked as an EMC/EMI engineer for 30 years. I could care less what some stupid paper says (might be misinterpreted anyway). Also did TEMPEST testing and hardening. Bet you didn't know we could read what you were printing from 200 feet away without shielding to TEMPEST specifications back then (that's EMI).
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.