Sorry for the delay in getting to your question.
When you get this kind of fault you need to check the carbon brushes in the back of the motor. As if they have worn down you will get this fault were the door locks but it wont start or it will but stop shortly after starting and the door lock light comes on.
To access them you need to remove the back panel and from there remove the motor from the bottom. At the back either side are the carbon brushes. Take these out and see if they have worn down. If so then they will need to be replaced.
So check them and if worn replace them and see how it goes from there. Fingers crossed that should cure it.
Let me know how it goes.