Hi, my girlfriend has just bought the Z3 and had the same issue.. Try removing any cases and covers and performing a soft reset on the handset (power button and volume up for two seconds until handset vibrates three times) then turn the phone back on. Run the diagnostic test again hopefully it should work. Well it fixed my girlfriends and has been fine since anyway. My thoughts are its a software issue not a hardware one but try to avoid cheap covers as these can put pressure on parts of the mobile if fitting too tightly. Hope this helps in anyway.
... View more