Why is my device using the 40NBT disconnecting from WiFi when scanning for a bluetooth connection?

The WB40NBT uses WiFi/BT Coexistence on the module. This disconnection is normal as the antennas on the device are saturated from the scanning and discovery process. WiFi will reestablish a connection when the Bluetooth scanning is complete. This happens because the BT portion of the radio requests access to the RF portion of the radio.  The request will have a priority associated with it depending on the type of request (tx, rx, scan, etc.).The WLAN portion will then either grant or deny access to the RF based on what it is currently doing and taking into account the priority of the BT request.