@d0d0 couple of weeks ago TP-Link released a new firmware for both A6 and C6 routers. I've updated all of my routers and no problem so far. I really hope they fixed the bug.

@StuartP I confirm this behavior on several Archer C6 and A6 routers which, I assume, are pretty similar. Seems that it is a firmware issue. Since it happens rarely and spontaneously it is hard to...