EX1 Backfocus Issues - I've sent two cameras back now

Has anyone else with their EX1 cameras come across a problem of slowly noticing your back focus is out, then over time (a day or two), the focus system fails altogether and the camera requires an OFF/ON to regain focus control again - until you change your zoom in which you lose focus again?

Today is the second time I have had to send an EX1 model camera back to the supplier from our production house (http://www.hsquared.tv). We've only owned the cameras for several months (since February)

The supplier claims not to have heard of this problem. Though in the first case, SONY replaced the lens system for us, but still we were down a camera for three weeks.

Be interested to hear responses - we have a third EX1 that has not shown this problem yet, though wondering whether to get it checked out in advance.

Cheers,
Tom

Camera Operator - Editor - Motion Graphics
(http://www.tomdavid.com.au)