Its completely stock 4.4.2 and while plugged into USB it becomes really really hot, battery discharges about 10% every minute or so and the screen flickers and can't be used (Feels like 100% cpu usage).
When you go into running apps, you can't see it because it constantly refreshes the list, and when its plugged into a computer, it works for a few seconds and then stops responding.
It works perfectly while not charging, and can be charged using the magnetic plug (Dock). Plugging into stock charger USB, car usb, or a computer all results in a freeze up/100% cpu usage etc If the phone is completely off, it can charge up very slowly while using USB and does not get hot, however the fastest way to charger it is via the dock option.
This is Australian stock, and is the second phone he has had to do this, his first phone he bought in Nov 2013, updated it to a 4.3 build in December and it did a similar thing, got this late December 2013, and has lasted until now, and is unusable while connected to USB.
This means it can't be updated, backed up, rooted or anything and sony want it to be sent away for weeks. Has anyone had any similar problems or know of a solution. It doesn't feel like its a hardware thing, but possibly something has shorted in the plug.. Not sure?