Comment 16 for bug 1748565

In my case I have the same issue
4.15.0-15-generic #16-Ubuntu SMP Wed Apr 4 13:58:14 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux

If I type
 dmesg | grep -i bluetooth
I get:

[ 2.233539] usb 1-1.4: Product: DW375 Bluetooth Module
[ 35.812010] Bluetooth: Core ver 2.22
[ 35.812026] Bluetooth: HCI device and connection manager initialized
[ 35.812029] Bluetooth: HCI socket layer initialized
[ 35.812032] Bluetooth: L2CAP socket layer initialized
[ 35.812037] Bluetooth: SCO socket layer initialized
[ 36.487377] Bluetooth: BNEP (Ethernet Emulation) ver 1.3
[ 36.487378] Bluetooth: BNEP filters: protocol multicast
[ 36.487381] Bluetooth: BNEP socket layer initialized
[ 63.484470] Bluetooth: RFCOMM TTY layer initialized
[ 63.484478] Bluetooth: RFCOMM socket layer initialized
[ 63.484487] Bluetooth: RFCOMM ver 1.11
[ 460.003598] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 475.007411] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 490.005426] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 505.007211] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 520.003265] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 535.006019] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 550.002996] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 565.005810] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 580.006797] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 595.005627] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 610.005595] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 625.006373] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 640.005272] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 655.006210] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 670.007190] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 685.005978] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 700.003936] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 715.005885] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 730.002791] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 736.002704] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 751.005650] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 766.002556] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 781.005387] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 796.005311] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 811.003208] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 826.004147] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 841.001988] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 856.002863] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 871.006809] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 886.005745] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 901.005710] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 916.004466] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 931.006359] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 946.002300] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 961.005133] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 976.006140] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 996.003009] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 1011.001881] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 1026.005811] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 1041.007667] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 1056.003608] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 1071.005537] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 1086.005406] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 1101.005309] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 1116.006203] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 1121.023108] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 1137.006058] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 1152.006965] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 1167.006789] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 1182.003767] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 1197.005699] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 1212.005568] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 1227.007394] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 1242.006303] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 1257.007178] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 1272.004137] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 1287.005954] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 1302.003964] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 1317.002796] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 1332.003782] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 1347.007590] Bluetooth: hci0: last event is not cmd complete (0x0f)

the last lines are only present when I type
scan on at the prompt of
bluethootclt
However my system is not able to discover many of the bluethoot devices. I have tested against my phone and other linux laptop.

So the message **IS AFFECTING** the Bluetooth functioning since the system does not connect to many of the devices.