Wi-Fi connections stalling on AirPort Extreme with 7.6.3 firmware Marco.org
www.marco.org/2013/05/21/aebs-wifi-downgrade
From the page
Saved with the link. Notes from 2007 to 2016 are mostly the page's own words, so this is probably an excerpt.
I've been having this issue occasionally from my MacBook Pro at home. :-\