Random spindle movement while cutting

I have two generic 3018 cnc machines running g code generated by Easel then downloaded to an offline controller. I get random movements of the spindle that cut from one area to another without raising the z axis. I have bought “Faraday Tape” that was advertised to help stop EM interference which may have helped a bit but I still get these annoying unwanted random cuts. Is the problem interference or something else? Should I wrap the wires again, spindle and the stepper motors, or is there another method to eliminate this problem?
Thank you to all that answer.
John Baker

Could it be that your z axis is locking up or that the safety height is so high that the z axis is topping out and loosing steps, thus it then doesn’t lift to the correct height before moving in x,y?
Or possibly the coupler to the stepper/ lead screw it loose? Or the brass antibacklash nut is partially stripped?
Or that the grbl settings aren’t set correctly and excessive acceleration or Max plunge rate is set too high causing the stepper to lock up?
Or a loose wire for that z axis, or an overheating driver even?

Unfortunately there’s lots of possible root causes for the provided scenario on a 3018 :man_shrugging:

Thank you for your reply. Ill check all these possibilities.

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