Today I turned on my notebook and everything was somehow ok inside dmesg related to bluetooth. After that I turned off-on for some 15 times - every time with bluetooth error.

Bluetooth turned on inside Ubuntu settings:

dmesg | grep -i bluetooth
[    1.732360] Bluetooth: Core ver 2.21
[    1.732371] Bluetooth: HCI device and connection manager initialized
[    1.732373] Bluetooth: HCI socket layer initialized
[    1.732375] Bluetooth: L2CAP socket layer initialized
[    1.732380] Bluetooth: SCO socket layer initialized
[    1.743346] Bluetooth: hci0: Firmware revision 0.0 build 90 week 25 2015
[    1.848901] Bluetooth: HCI UART driver ver 2.3
[    1.848904] Bluetooth: HCI UART protocol H4 registered
[    1.848906] Bluetooth: HCI UART protocol BCSP registered
[    1.848907] Bluetooth: HCI UART protocol LL registered
[    1.848908] Bluetooth: HCI UART protocol ATH3K registered
[    1.848909] Bluetooth: HCI UART protocol Three-wire (H5) registered
[    1.848932] Bluetooth: HCI UART protocol Intel registered
[    1.848945] Bluetooth: HCI UART protocol BCM registered
[    1.848946] Bluetooth: HCI UART protocol QCA registered
[    2.831762] Bluetooth: BNEP (Ethernet Emulation) ver 1.3
[    2.831764] Bluetooth: BNEP filters: protocol multicast
[    2.831768] Bluetooth: BNEP socket layer initialized
[    4.928101] Bluetooth: RFCOMM TTY layer initialized
[    4.928178] Bluetooth: RFCOMM socket layer initialized
[    4.928182] Bluetooth: RFCOMM ver 1.11

Bluetooth turned off inside Ubuntu settings:

dmesg | grep -i bluetooth
[    1.874571] Bluetooth: Core ver 2.21
[    1.874584] Bluetooth: HCI device and connection manager initialized
[    1.874587] Bluetooth: HCI socket layer initialized
[    1.874589] Bluetooth: L2CAP socket layer initialized
[    1.874596] Bluetooth: SCO socket layer initialized
[    1.884772] Bluetooth: HCI UART driver ver 2.3
[    1.884774] Bluetooth: HCI UART protocol H4 registered
[    1.884775] Bluetooth: HCI UART protocol BCSP registered
[    1.884776] Bluetooth: HCI UART protocol LL registered
[    1.884777] Bluetooth: HCI UART protocol ATH3K registered
[    1.884779] Bluetooth: HCI UART protocol Three-wire (H5) registered
[    1.884800] Bluetooth: HCI UART protocol Intel registered
[    1.884811] Bluetooth: HCI UART protocol BCM registered
[    1.884812] Bluetooth: HCI UART protocol QCA registered
[    2.018145] Bluetooth: hci0: Bootloader revision 0.0 build 2 week 52 2014
[    2.023135] Bluetooth: hci0: Device revision is 5
[    2.023138] Bluetooth: hci0: Secure boot is enabled
[    2.023139] Bluetooth: hci0: OTP lock is enabled
[    2.023140] Bluetooth: hci0: API lock is enabled
[    2.023140] Bluetooth: hci0: Debug lock is disabled
[    2.023141] Bluetooth: hci0: Minimum firmware build 1 week 10 2014
[    2.039100] Bluetooth: hci0: Found device firmware: intel/ibt-11-5.sfi
[    2.063532] Bluetooth: hci0: Failed to send firmware data (-38)
[    4.066208] Bluetooth: hci0 command 0xfc05 tx timeout
[    4.225754] Bluetooth: BNEP (Ethernet Emulation) ver 1.3
[    4.225757] Bluetooth: BNEP filters: protocol multicast
[    4.225759] Bluetooth: BNEP socket layer initialized
[    8.944807] Bluetooth: hci0: Reading Intel version information failed (-19)
[    9.346262] Bluetooth: hci0: Bootloader revision 0.0 build 2 week 52 2014
[    9.351267] Bluetooth: hci0: Device revision is 5
[    9.351269] Bluetooth: hci0: Secure boot is enabled
[    9.351270] Bluetooth: hci0: OTP lock is enabled
[    9.351287] Bluetooth: hci0: API lock is enabled
[    9.351288] Bluetooth: hci0: Debug lock is disabled
[    9.351289] Bluetooth: hci0: Minimum firmware build 1 week 10 2014
[    9.351433] Bluetooth: hci0: Found device firmware: intel/ibt-11-5.sfi
[   10.715096] Bluetooth: hci0: Waiting for firmware download to complete
[   10.715250] Bluetooth: hci0: Firmware loaded in 1337743 usecs
[   10.715320] Bluetooth: hci0: Waiting for device to boot
[   10.727323] Bluetooth: hci0: Device booted in 11762 usecs
[   10.730228] Bluetooth: hci0: Found Intel DDC parameters: intel/ibt-11-5.ddc
[   10.732332] Bluetooth: hci0: Applying Intel DDC parameters completed
[   10.733322] Bluetooth: hci0: Setting Intel event mask failed (-16)
[   10.788864] Bluetooth: RFCOMM TTY layer initialized
[   10.788883] Bluetooth: RFCOMM socket layer initialized
[   10.788886] Bluetooth: RFCOMM ver 1.11