Voltage issues on Shelly EM

Hi all.

I'm new in this forum. My name is Daniel and I'm writing from Spain.

I'm mounting solar, domotics and EV infrastructure at home

I was looking for last few days but didn't find anything about want issues I'm experiencing with my 2 EM units. Both devices are measuring voltage over real. Loads measurements are very close instead.

I'm measuring grid voltage with a Carlo Gavazzi 112 and, under any load condition , is 5-7 volts under the Shelly's measurements.

Is there any way to fix this?

Thanks in advance.