I have two of these Panasonic KX-TG8323 phone sets:

One set purchased in January 2011 and then another added in April. They were perfect until the LCD displays on two of the January handsets started pulsing. It's the back-light intensity stepping up and down (it's abrupt steps, not fading in/out). The cycle is on average just a little quicker than 1 second, but the speed and intensity of the pulsing seems to vary slightly (sometimes it's more noticeable than others). If I pick up the handset and re-set it on it's cradle, the display is steady for a just over a minute, then the fluctuations resume.

- I've tried the handsets in other base units/charging cradles (and other handsets in the 'faulty' handsets original cradle), and the problem follows the handsets.
- I've cleaned the contacts on the handsets.
- I've tried swapping the batteries from other unaffected handsets.

I don't suppose anyone has any ideas on what might be causing this or how I can fix it? I was going to return them until I noticed that the warranty was only 1 year.