Ultimate guidance to avoid Electromagnetic Interference

More information please. 
What plasma cutter (with URL for it)?
What control hardware?
What sized motors?
What voltage for motors?
What power supplies are you using in the control box?
What Plasmac Mode?
How are you obtaining an ArcOK?

If you run that job with the torch disabled, does it follow the correct path?

Thanks for reply Mr.Rod
1.stahwerk cut 70 igbt
2.2x breakoutboards
3.3Nm stepper motors
4.36V DC
5.Act motor psu-s
4.latest plasmaC
Yes with torch disabled it runs perfectly . i have dual configs with mach 3 and PlasmaC , perfectly on both.
Attached some pictures to make it more clear.
regards Shpat

Today ill order new plasma of CNC stamos s85 , will change the cables of motors to shielded ones , will change the power supply cable of my shop from 5G2.5 copper to 4x25 alu ,Will add a mesa controller , if this doesnt solve this problem ill definetely sell this machine for scrap.

Looks like its a HF start machine?
Lower voltage on the BOBs is not helping.
Make sure you use 24V with the mesa for greater noise immunity.
Move your PC away from the control box as the ethernet cable will add more isolation
Add a RFI filter to the mains power entering the control box.
Try and run your shielded stepper cables right to the stepper drive and ground the shield right there.
Try and earth to the motor across to your existing earths.
 

Thank You for Your help mr.Rod.

Just found this pic. Notice the grounding point. There must be a reason for it...