Just stumbled on this today so a bit late. I believe the test equipment is correct since the electronic load and power supply agree. First thing I would suspect, since the reading is exactly double, is that the shunt is the wrong one. Maybe the shunt is for 100A but the meter is expecting a shunt for 200A. Since the voltage drop across the shunt (what is being measured by the meter) is double what it should be because the shunt has twice the resistance, it is showing double the current reading on the LCD. I would suspect if the wiring was the wrong size, you would get some other non-related current measurement.
tgerbic