升级到 18.x 蓝牙问题：hci0: last event is not cmd complete (0x0f)

由于我已经升级了 Ubuntu 18.04（以及之后升级到 18.10），我遇到了蓝牙连接问题。例如，我的蓝牙扬声器播放的音乐严重滞后。经过调查dmesg，我遇到了很多这些错误：

Bluetooth: hci0: last event is not cmd complete (0x0f)

我尝试bluez通过官方 PPA 更新（5.48 -> 5.50），但这没有成功。

输出自lsusb | grep Blue

Bus 006 Device 003: ID 0930:0508 Toshiba Corp. Integrated Bluetooth HCI

奇怪的是，执行时我有 2 个蓝牙设备列表rfkill list

0: Toshiba Bluetooth: Bluetooth
    Soft blocked: no
    Hard blocked: no
1: phy0: Wireless LAN
    Soft blocked: no
    Hard blocked: no
2: hci0: Bluetooth
    Soft blocked: no
    Hard blocked: no

的输出dmesg | egrep -i 'blue|firm'可能表明固件存在一些问题：

[    0.069143] acpi PNP0A08:00: [Firmware Info]: MMCONFIG for domain 0000 [bus 00-3f] only partially covers this bridge
[   18.813225] toshiba_bluetooth: Toshiba ACPI Bluetooth device driver
[   19.651213] iwl4965 0000:01:00.0: loaded firmware version 228.61.2.24
[   55.834864] iwl4965 0000:01:00.0: Enabling power save might cause firmware crashes
[ 1204.278716] Bluetooth: Core ver 2.22
[ 1204.278758] Bluetooth: HCI device and connection manager initialized
[ 1204.278764] Bluetooth: HCI socket layer initialized
[ 1204.278771] Bluetooth: L2CAP socket layer initialized
[ 1204.278783] Bluetooth: SCO socket layer initialized
[ 1204.664153] Bluetooth: BNEP (Ethernet Emulation) ver 1.3
[ 1204.664155] Bluetooth: BNEP filters: protocol multicast
[ 1204.664162] Bluetooth: BNEP socket layer initialized
[ 1204.769152] Bluetooth: RFCOMM TTY layer initialized
[ 1204.769161] Bluetooth: RFCOMM socket layer initialized
[ 1204.769172] Bluetooth: RFCOMM ver 1.11

我的内核版本：

4.18.0-10-generic

请问我该如何解决？