Theres a couple of things that can causes this fault. Theres the door lock and wiring to the lock, worn carbon brushes in the motor or the main control board.
The first thing to check is the door lock. Unplug the washer and open the door and remove the metal clamp around the door and unlip the door seal.
Then you can remove the door lock and pull it through the port hole.
Disconnect the wiring block and inspect the wiring block and see if theres signs of burning on there. If so then the lock will need to be replaced and the wiring blocked repaired. You can cut each wire out and retag the wires on there own.
If the door lock and wiring looks ok then you need a multi meter to test the lock. On there you will see 3 tags. Test beteen them all for contonuity and you should get a reading between 2 of them. If you dont then the lock is faulty and will need to be replaced.
But if the wiring and the door lock are fine then you need to remove the motor at the back at the bottom.
There at the back of the motor you will see the carbon brushes (if fitted as not all versions of this model use them)
If the carbon brushes are there remove them and see if they have worn. If so then you need to replace them.
But if the brushes are fine or your version hasnt got them then its going to be the main circuit board at fault here.
If you need anymore info just get back to me.