Ok what this may be is worn brushes in the motor. As when they go you get the fault with the door lock light coming on. So if they are very worn they can still just about tunr the drum but will cause it to play up like its doing now.
To check you need to pull the washer out and lean it backwards against a wall and get someone to hold for you.
Then lay down and look under the washer.
There at the back of the motor either side you will see the carbons.
Take them out from the motor and see if they have worn down.
If so then replace them and see how it goes from there.
Fingers crossed its just worn brushes.
But if they are fine then its either the motor itself or the control board which both of these are very expensive and on an 8 year old washer isn't worth fixing im afraid as you could get a new washer for not much more then the parts are on yours.
But well worth checking the carbon brushes first as it may just be them and they are easy to fix and are about £20 for the pair.
If you need anymore info just get back to me.