Maybe look at the raw numbers.
If your A+/A- input voltage is bigger than 20mv (40mV?) then the amp will peg at one end of it's range about you'll be calibrating between nearly constant raw numbers, making the slope of the calibration be random.
Tha result looks like the wiring of the bridge is shorting the E+ to E-. Sometimes the colors are wrong on the load cells. Disconnect the load cells completely and check that the resistance from black-to-while is 2000 ohms, and from black to red =1000 ohms, and white to-red=1000 ohms on each of them. Red should the middle of the half-bridge. If not, whatever are the middles of the half-bridges should connect to A+/A-.