How can I fix my LG WM-16110FD washing machine?

Hi, this may be something simple. I really can't afford an engineer at the moment. Everytime I put the wash on it flashes that the door isn't shut when actually it is. With a lot of fiddling about, eg. holding the door in, turning off, resetting etc. I am just about able to get it to go, but I just know that one day it won't, and I can't afford to be without it. Any ideas I would be really grateful. Even though I am only a woman I am great at fixing things if I have a rough idea of what to do. Thank you for reading this. Jackie