What else would it be if not the espresso machine? My thermometer has been calibrated, so I’m pretty sure it’s not that but I am going to experiment again with a different thermometer just to be sure.
Please correct me if I’m wrong, but if there is steam coming out from the group, that should tell me that the water in the boiler has reached it’s boiling point (around 204 at my elevation) yet the GB5 says it’s at 211 degrees, but that can’t be possible, right?