Our devices We have a household with two MacBook Pro's (one Sierra, one El Capitan), and iPhone 7 and an Android Nexus 6. The problem Yesterday, seemingly out of the blue, the WiFi stopped working for my wife. When we investigated, it turned out that every time she connects her MacBook Pro to the WiFi router, the WiFi connection drops for all devices. Resetting the WiFi router resolves the problem and if her MacBook Pro is not on the network, all other devices work flawlessly. If her MacBook Pro connects, WiFi works briefly (20 seconds or so), even on her MacBook Pro, but then breaks again. A strange symptom One other strange and possibly related thing: we've noticed is that System Preferences is now often hanging on her MacBook Pro when WiFi is on. Not having seen System Preferences hang in 10 years of Macbook use, I thought this was a little suspicious. Tried so far I've tried to find help online, but most articles deal with WiFi issues dealing with one device. I've following this page's instructions (minus resetting SMC or PRAM) to no avail. Does anyone know possible causes for a MacBook Pro bringing down the WiFi network for all other connected devices? Thank you!