Hi, the buttons on top of the machine are not designed to turn off the machine. One is meant to be used to cancel the current print. The other only turns the screen module off. There is no hardware present to turn the whole machine off except the power switch on the back.
This is not a bug and is working as described in the manual.
Although i do agree that the power switch is rather inaccessible. The machine is meant to run 24/7.