On Friday, when placing the mirror in the mount inside the cavity, the mirror is fixed using a ring with 3 screws

one of the screws fell through the holes connecting the breadboard to the box (managed to remove it, but there was a lot of dust and metal particles left after)

cleaned the inside of the box, careful in the future.

There are only 3 for each mirror, it seems there are no spares. Careful not to lose them