I have one and the power supply lines (to the glitching CPU) seem stable with minimal noise. The CPU-integrated USB2 PHY also retains its connection even during the CPU glitch. A connected Linux workstation will not log any USB connection or disconnection events. And a CDC serial connection will remain open. The power levels to the stepper driver chips also remain stable during the glitch.
So to me, it looks like the glitching happens exclusively inside the CPU. It appears that I’m randomly experiencing the exact same issue that the PicoEMP in the original article can induce.
Next steps: EMI (near field) probes for your scope.
https://www.rohde-schwarz.com/us/products/test-and-measureme...
are you sure it is not just the nemas causing a under voltage situation?
Just a reminder to ensure that you have brownout detection enabled on the CPU/MCU (assuming it's available) and are checking for it in your firmware. Supply drops can be very brief.