Hello routercnc,

Thanks for your message. It is very interesting what you are explaining. It's something I haven't tried yet, plugging the VFD into a complete different socket out of my room. As you can see on the pictures, the room is pretty small, so there might be something there.

You are right about the BOB's signal cables. STEP and DIR are CY-2 0.5mm^2. The shield is not earthed. I know I should, this was just really me trying to get minimal connections.

I think you're right with the process, as others have suggested. So here's what I think I'll do:
1. try power the VFD from a socket located in another "block" of my house (one that's on a different breaker circuit).
2. If the above doesn't work, I'll put an EMI filter on the mains of the VFD (or inverter as you call it)
3. If that doesn't help, I'll buy spare BOBs from China.