Many people have experienced a bug whereby the Sony Xperia Z3C (compact) no longer has functional home and back buttons. Specifically, the issue involves the buttons highlighted by the red rectangular box in the following image:
The problem may be caused by a number of reasons, from hardware issues to software upgrades. A solution is not easily found. As these buttons are essential for using the phone, when they are broken the phone is far less usable.
A quick workaround is to rotate the phone "upside down" so that the buttons flip to the "top" of the screen.
How do you fix this issue permanently?