Update
My 2014 LR4 HSE has now experienced this issue 9 times. Mostly occurs when accelerating from a stop or near stop. It is so quick you could miss it (except that the audio from the stereo cuts out and the headlights turn off, then back on).
Apparently Land Rover has been investigating the issue for over a year and has no idea what causes it and thus no proposed fix. I have been asked to document all electrical use when the issue occurs (and have replicated the issue with ECO on/of, seat heaters on/of, heated steering wheel on/of, satellite radio, iPod, bluetooth on/off).
The LR4 goes back to the dealer today (after 4 occurrences yesterday and today) so they can pull whatever data is on the computer and provide the same to Land Rover to help engineering identify the issue and a potential fix.
Slightly frustrated with my 4 week old purchase of a 2014 HSE... and my new position as advisor/guinea pig to Land Rover engineering. Good thing my first payment is due in a few days and I'll have a loaner LR2 while paying for a well equipped LR4. Ugggh.
Craig