|This sounds like a router issue.|
Check to ensure the router has the most up-to-date firmware. If it doesn't, update it.
If that doesn't fix the issue, try resetting the unit to factory defaults (as per the setup guide/manual) and reconfigure it.
If that doesn't fix the issue, chances are the unit is in need of replacement.
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.