He was pushed for time so didn't run any tests via the power outlet but tested the circuit (turned off the circuit at the main board) and asked if i had tried connecting the TV to a circuit outside the one he turned off and i have, in fact i have tried several power outlets throughout the house with no improvement.Just a wild thought - you live in New Zealand. I have visited there many times and have loads of friends out there. One thing I do remember was that some have complained over the years about the quality of their mains electricity supply. I think you said on another thread that you had an electrician check things but how far did he go? Modern power supplies are very tolerant of voltage and frequency variations but do not tolerate departures from sinusoidal waveforms too well. Also additional interference on mains could upset the power supply in the TV. This may be intermittent and therefore account for the changes you observe.
But yes, to me it seems to be an intermittent power problem as i eliminated the devices in the past by disconnecting them all and hard resetting the TV with no improvement.