S Class 2002 Convenience open close help required please.
 

I have an intermittent problem with the convenience open and closing feature on my s-class which is a pain. If you get out of the car and leave a window open sometimes you can close it with the remote sometimes not. The car does not have keyless go. If I hold the key very close to the IR sensor in the passenger door it usually always works, but not on the drivers door. Any suggestions would be appreciated. Oh, and I have replaced the batteries in the remote to no avail!