maybe this router machine wireless sensitivity mechanism got problem (the 2.4ghz part) or the receiving hardware sensitivity problem

as suggested, try update your router firmware first & choose different channel, and also update your reception hardware driver.

if can, use other receiving point such as laptop, phone to determine if same problem happens when go downstairs. in order to confirm if it is the router own problem. if firmware update cannot solve, need to RMA router warranty.

This post has been edited by coolstore: Mar 16 2016, 10:55 AM

the last thing u can do before send for warranty:

put the router at different spot to test, maybe this time at downstair, then u walk upstair, is that problem exist again

or choose not your present place to c, such as your friend house where he got similar router, just test side by side then can confirm router problem already.

since this is dual band router, not very extraordinary if either band got problem since its hardware is using 2 different band wireless amplifier inside.