Your configuration allows 4.5x Ie as the starting current limit. If you are tripping on high starting current of >1200A, then you likely have a very large starting torque requirement or a locked rotor. Are you starting with a high connected load? Does the motor start to turn when the start command is given? If you disconnect the motor coupling, can you spin the motor by hand? If not, the motor may be mechanically locked or bound.
I would three things. First, verify the nameplate data on the motor to insure you have the motor you think you do. Sounds silly, but I have seen it happen many times. Also make sure that the motor is properly sized for the load. This happens a lot on new installations where the assumed load size calculated by the engineering company is not what is reality in the field.
Second, put a clamp-on ammeter on one phase of the output power to the motor with the "max current value" capture feature on, if available. Verify that you are really sending 1200A through the circuit (400A per phase) when the motor starts.
Second, set the Phase Imb Level to max (8o%) and the start ramp to 30 seconds to see what happens.
Lastly. this may be one of those rare instances you will need to install a larger soft starter (larger kW capacity).