IF IT WORKS, DON'T FIX IT!
Placement of the router is crucial to good operation and coverage with in the building. Central and on the main floor is preferred.
Other problems can be caused by external conditions as well.
Any cordless house phones?
Any other WiFi routers in the area? Link> Use
InSSIDer to find out. How many?
If your wanting more coverage along with using the 825, I recommend reviewing these to maybe include with in your building:
D-Link DAP 1360, 1513, 1522, 1525, 1533 series are some of the home and small business class devices.