Remote key

Only one of the keys on my X Type operates the remote locking now. Problem I have is that it will operarate the remote locks for about a week or so and then stops. I can rectify this by going through the reprogramming process for remotes and it is then OK for another week before it stops working again. I had the remote itself repaired a couple of years back and yes have changed the battery. Is the remote in need of a further repair?