Ahh yes, I know what you mean and I have planned ahead for that, but I still have the Kress installed. It happens when the 25pin cable is connected to the PC (at the PC end) whether or not the PC is on. I also tried it in the standard printer port & same thing happens. Also happens with my spare PC.

It does look like electrical noise and it's on all axis. I just can't see what has changed.