I have to say, my 650 is the most fickle phone for connectivity (Wi-Fi, Bluetooth, cell data) of all the phones I've worked with. I have factory reset several times. Reboot constantly. I am not sure if it's the chipset in the phone, or a driver issue.
The Wi-Fi, gets stuck in low signal strength, even though I'm in the same room with the base station. The phone will try to get data via Wi-Fi, fail, go with Cell data, then flip flop back and forth till it times out. If I turn off and on Wi-Fi things starts working. If I can turn back on Wi-Fi... Sometimes the slider for turning on/off Wi-Fi disappears in the settings screen.
I have found the Bluetooth side to be somewhat non-standard and very frustrating, meaning it doesn't work with some Bluetooth devices even though everything else will. And all the features of Music, Voice, Cortana don't always work, even though my older Windows Phone/Mobile devices worked perfectly. Or if I have a Bluetooth device that does work as it should, when I turn on the device, the 650 will connect and work fine, then if I turn off the device, wait a bit, turn back on the device the 650 won't connect back up. Some times toggling off/on the Bluetooth on the 650 fixes it. Other times, I can turn off the Bluetooth, then the slider for Off/On disappears just like the Wi-Fi issue. I have to reboot to get them back.
I am so tempted to see if someone wants to trade me for an unlocked 640 with Windows 10 Mobile....