This is most likely to the lock mechanism, its probably sensing the door is closed, then activating the lock (which doesnt fully engage) and then throws an error.
It may be another sensor causing the issue, buts its unlikely to be the main PCB, are any error codes shown on the display?
Please let me know if you need anything clarified.
This would suggest a door lock fault then, if there was a sensor failure it would most certainly generate a error code.
A replacement door lock would be around £15 in parts, its not an overly complicated part to change however if you would like me to recommend an engineer to replace this for you please provide your post code.