What can cause the door that drops the grounds into the tray to get stuck and not go back into position? We have been able to reset it by making a cup without the bin part of the tray and the grounds drop directly into the bottom tray, but how does it get stuck to start with? We have an older Impressa F9 machine. It is cleaned whenever it tells us to. Could it need decalcifying? Can we force it to run the decalcifying routine? Thanks.