Im experiencing the exact same issue with the i5 NUC and the 7260 card, both Intel. Bluetooth works from a cold boot after the Power Supply is disconnected completely and re conneted. after 1 or more sleep session, it appears to start acting wonky. A warm os/bios reboot doesn't seem to fix the problem... Also, device does not seem capable of remote wake from a bluetooth keyboard.
Please fix this problem, as i now need to go buy USB Bluetooth dongles to work around this.
file under #intelfail (on an otherwise great product)