Read this history first so you to help you understand operation.
I fixed this problem for a friend a few weeks ago (mostly by phone).
His original problem started when EM switch fell apart and something went to ground.
This destroyed everything that ran on 5 volts, and blew the tracks off the main board near the power transformer.
All electronic boards were damaged.
He replaced the lot, and with newer versions, and nothing worked.
He rang me, and after hearing the history, I got him to measure the 5v feeding to the hall sensors. (green plug at end of big board)
He had 5v. When you measure the output from the hall sensors, (3 terminals near the end), at any time any 1 or 2 should measure 0v.
Likewise any 1 or 2 (of the three) should measure 5v.
When you rotate the spindle by hand these should all change alternately.
In summary. ALL should never be 5v or 0v. Thats when you get the ERR message. The motor controller doesn't want to turn on all 3 phases at once! and rightly so.
Normally if you rotate the spindle by hand when it is powered up, it should read 10 or 20 on the readout.
ALL OF THE HALL SENSORS WERE NOT WORKING. They are in the end of the motor.
He bought the motor to me, I replaced the sensors, and tested the motor.
He took it home and his machine was used for a couple of hours. Looks like I fixed it, but he left it on not running for a few hours, then the big control board died. Fault not known. 5v OK Hall sensors still work. He is 80Km from me. He took it back to supplier. I don't know result yet.
This is some recent history.
As your motor rotates a part of a turn, at least one of your hall sensor signals is OK
Because it still tries to run, first check for one of the hall sensor wires having an intermittent connection. Chinese workers using wrong crimping tools is a known problem.
If all of your HALL SENSOR signals are working, then one of the 3 phase wires, U,V,W may be open, or a fault in the motor controller 3 phase H-Bridge or hall sensor signal problem ON THE MAIN BOARD.
Sorry about long answer, but that should answer just about any issue with this problem.