Right, I'm having trouble trying to shut the sliding door. When I pull it shut, it wants to spring open at the back, almost as if the spring is too strong and the only way to close it is to push it shut and inwards from the back. Shutting it from the inside is an impossibility. Nothing is catching, and I've recently fitted a new plastic sliding block/guide thing which sits in the track but didn't make any difference. Any ides? Thanks.