Keyfob has become slow to unlock my Mondeo

A year ago my keyfob began to take several goes to lock/unlock the car. The main dealer changed the battery (in the fob) but the problem persists. Is it easily fixed, or does it imply the sort of bill...

Mondeo won't lock

I have a 2002 Mondeo but the central locking won't lock when using the fob, yet it works fine with the key. By this I mean if u use the fob it just unlocks itself straight away after locking.

I've replaced the batteries in my keys but the car still says low battery

I have replaced my key fob batteries on a couple of occasions but it still indicates that the battery is low. Am i missing something here that i should do after installing new batteries?