Does anyone have any suggestions on how to securely lock the external door of my 2007 Elddis Crusader Superstorm from the inside at night, I have a young family and even my 2 year old, who does occasionally sleepwalk, can open the external door even when in the 'up' or 'locked' position... i'm petrified of one of them doing this in the middle of the night and wandering outside, any suggestions gratefully received.