yes, i think itīs a hardware problem.
when you disassemble the g4 unit and have a look to the buttons, you see, the key technics is like a old remote control from a television. (Folie) i think you have a problem with "one of the buttons is always pushed" (not really mechanical stable - the construction)
sometimes you have the same thinks like this, when a button always pressed e.g. press the vol_up button and the vol_down or the Mute in same task.
send it back, if you have warranty. and dont use that buttons often. better you use the touchscreen buttons or the remote control.
please let me know, if you fixed that problem.
maybe it can helps, when you open your g4 front panel, and place (fix) the circuit with the button electronic to the right place ;-)