I had a strange issue today.
After removing a printed chamber and cleaned out the printer.
I was about to start another when i noticed the door did not lock in place.
I checked the latch if it was crooked etc. Looked pretty good.
After troubleshooting connectors on the inside of the locking mechanism inside the printer. I disconnected and reconnected. All seated perfectly.
I did several restarts, ended up doing a powercycle.
Voila, the lock works again. So the printer most likely just had a software hickup.
Most importantly, do NOT unscrew the latch as the backplate will come off and you will have to separate the door and the inner lining to get it out and back in place. (Don´t ask me how i know this) 