Progressive Industries Hardwired EMS/Surge Protectors
Each unit includes a digital display, scrolling continuously through the power source information: Voltage(s), current, frequency, error code, and previous error code (if applicable). Information for BOTH legs
First L1
Then L2
Voltage measured at power pole.......
Did 'electrician' measure L1 to Ground, L1 to Neutral, L2 to ground, L2 to Neutral, L1 to L2 ???
Or just measure ONE leg and call it good?

Got access to a different 50A source......??
Measure the voltage at receptacle and compare that with your EMS Display