RT-AC86U powers up to Internet red led, then powers off

Had one of my RT-AC86U's stop working after a few months of great operation. Powered off/on but at the boot up point to where the red internet led comes on, unit then powers off. You can repeat this circle as often as you want, until you get bored and stop.
Put router into firmware recovery mode and loaded the latest ASUS firmware, successfully. But alias the same issue afterwards. Also tried Merlin's code, also the same power issue.
Phoned ASUS support, will replace the unit as a known...

RT-AC86U powers up to Internet red led, then powers off