Hi Beckle,

The Crystal ball is in Lockdown so we need more info from you first before we can really help. You haven't mentioned anything about what you have in the electrical box or how you have wired it.

Pictures of inside the control box and of the machine in general will help massively.

Tell us about the controller your using and the voltages your using. What exactly is the EMF affecting.? E-stop, limits, PC, etc

Do you have the frame grounded.? and have you used Star grounding.?
Where is the VFD grounded and are you using screened cable also is the Screen grounded and where too.

The more Info and pics you give the easier it will be to find the issue.