" in device manager window

I tried to update the bluetooth driver, but it seems all bluetooth drivers are up to date.

I also checked services and Bluetooth Support Service and Bluetooth Handsfree Service are running and they run automatically as the laptop starts up.

When I restart the laptop twice or three times, the bluetooth toggle button appears and it works fine. However, it disappears when I "sleep" the laptop and recover it from the sleep. 

I suspect that it might something to do with connecting/disconnecting to/from Dell Thunderbolt™ Dock (I use the laptop at work, and unplug Dock cable and bring it back home every day), but not quite sure.