So you use the BLX Esc with the BLS 2-pole 4000kV motor?
Could be a problem with the Esc, but it might be a timing problem. Since this cannot be adjusted with the Arrma Esc there are no options to check this.
Do you have any other brushless motor you can check?
And, I have heard this might work - have not tested it myself, you could swap the motor leads around: Unplug and put in another lead from the Esc so they all get mixed up. And in case the motor turn backwards, swap any pair (2 out of the 3 leads) again to make it run forward.