The lack of automatic opening of the valve when printing, you must open it manually imperative
non possibility of closing the valve of the sheet loading tray, if you want close, remove all the leaves (not practical at all, and more dust gets inside when everything is open
Finally, when printing, do not forget to thoroughly disengage the outlet valve of the printed sheets and including opening the hinged support at the loading tray, otherwise everything falls !!!!
A long-awaited improvement in light of comments