Dell Inspiron 15 7527: Wireless and Bluetooth missing

Intel Wireless N-7260 is known to have issues, but it worked ok for me after I uninstalled the drivers and let Windows install a driver automatically. It worked fine for more than 7 months.

But few days ago, suddenly something happened. When I start the laptop, it shows the wireless connection for few seconds, but then wifi just vanished. There's an icon appearing in "Control Panel\Network and Internet\Network Connections", but doesn't appear in the network sidebar of Windows 8.1.

Dell's System Checkup says WiFi isn't turned on.

I re-installed Windows via recovery, still the same problem.
Then I noticed another thing. Bluetooth is also gone. Doesn't even appear in Device Manager.

However, "Intel(R) Wireless-N 7260 still appears in the Device Manager. When I uninstall driver in there and let it scan for hardware changes, wifi works again. But after signing out or shutting down, there will be the same problem and I have to do that uninstall-scan hardware change process again to get it work. Bluetooth is still gone.

Is there a hardware failure, or there is any software fix?