Something to do with placing that disc in the door when it was open.
So they moved the blue disc to open the doors, neglected to use the lever so the next blue disc would be available.
Then they shuffled those other 2 brown discs for some reason, placing 1 in the doorway.
They then moved that blue disc off the mark and the doors closed but the disc stopped it.
Finally resting the blue disc where it is and dragging the brown stone out of the doorway and thus the pic. 🤔