Could possibly be the latch on the door handle. Try pushing the door in a bit or get your fingers behind the handle thingy and make sure it's closing properly.
Had this problem with my mam's a while back. Easy fixed with a new handle or even just wedging a bit of cardboard or sommat behind the handle.
Had this problem with my mam's a while back. Easy fixed with a new handle or even just wedging a bit of cardboard or sommat behind the handle.