|It's entirely possible the router is having issues or failing. Since you've tried rebooting it and the problem persists I would now recommend checking for newer firmware and if newer is available, apply it to your router.|
If that fixes the issue, great. If not, you'll probably need to replace the unit.
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.