RT-AC68U Wireless turning itself off?

Hi,

I have a problem with my RT-AC68U, it's been solid as a rock for over a year with Merlin's firmware on it. Yesterday it started randomly turning both it's wireless antennas off.

I logged in over a wired connection, re-enable both in Wireless -> Professional and away I go, but within 5-10 minutes it's re-disabled itself!

I've tried rebooting, nothing has changed in my setup. It doesn't feel hot to the touch. Anyone any ideas?

Thanks

James