A number of users have been complaining about the back panel glass, which has lifted slightly on one side. Some people are concerned that the phone has lost its water resistance due to the raised panel. For most users it hasn’t caused any issues, but for others it has led to the water resistant indicators on the ports turning red – even if all of the flaps had been closed.
The issue seems to happen either in hot weather or when the phone is being stressed heavily through gaming or other high intensity tasks. This causes the phone to heat up and the theory is that this leads the glue holding the back panel in place to melt. It affects the top half of the handset on the left side – where the Snapdragon chipset resides.
The problem with this type of issue is that Sony repair centres are turning people back, judging by comments on forums. Repair centres have no way of telling if water damage has been caused by a loose back panel or whether someone has inadvertently left a flap open.
People are taking the issue into their own hands by using a hair dryer to melt the glue, push the glass back in, clamp it in place and then wait for the glue to cool down. Others have applied glue externally around the edges as a temporary fix.
This has happened to my Z (although I wouldn't have known unless I looked for it.) The back glass is raised slightly on the top left side. Seems to be a serious problem as users on Sony blogs and XDA report that their phones are no longer waterproof.
I'm not bothered myself as I don't use the Z as my daily driver, but I would advise anyone not to buy this phone as it is a defect and is just a matter of time (and heat) before the glue fails.