X3i System ?

The X3i system use to show the caller on caller display this is on both hand sets, but now only does it now and again and sometimes not at all, is there somthing i can do my self to give a constant caller display as it should be.I have removed the battery to try to rest the Phones, and also removed every detail and reinstalled but even this as not helped, can you please help. Thank you Frustrated!!!