Ubuntu – Bluetooth connection (Bluez) not working after logout (works after restart)

I use LXQT in Lubuntu 18.10 and I have a problem with keeping the Bluetooth-speaker connected to the laptop after logging out and in. It works fine after reboot though.

So, I have a solution that always works: rebooting – OR: reinstalling bluez:

sudo apt-get install --reinstall bluez

and that always works!

In any case, when my problem happens, the bluetooth is never blocked.

If I reboot or reinstall bluez there is no need to remove and add again the device, setting it to "Audio sink" is enough.

When this happens, after logging out and in:

• The speaker is listed by blueman-manager, setting to 'Audio Sink' brings the error Protocol Not available.

In terminal:

~$ blueman-manager
_________
Load (/usr/lib/python3/dist-packages/blueman/main/PluginManager.py:60)
['PulseAudioProfile', 'Services'] 
_________
__load_plugin (/usr/lib/python3/dist-packages/blueman/main/PluginManager.py:133)
loading <class 'blueman.plugins.manager.PulseAudioProfile.PulseAudioProfile'> 
_________
pa_context_event (/usr/lib/python3/dist-packages/blueman/main/PulseAudioUtils.py:341)
1 
_________
__load_plugin (/usr/lib/python3/dist-packages/blueman/main/PluginManager.py:133)
loading <class 'blueman.plugins.manager.Services.Services'> 
blueman-manager version 2.0.5 starting
Stale PID, overwriting
_________
pa_context_event (/usr/lib/python3/dist-packages/blueman/main/PulseAudioUtils.py:341)
2 
_________
on_bluez_name_owner_changed (/usr/bin/blueman-manager:96)
org.bluez owner changed to  :1.238 
_________
get_interface_version (/usr/lib/python3/dist-packages/blueman/bluez/BlueZInterface.py:13)
Detected BlueZ 5 
_________
SetAdapter (/usr/lib/python3/dist-packages/blueman/gui/DeviceList.py:271)

_________
on_adapter_changed (/usr/lib/python3/dist-packages/blueman/gui/manager/ManagerToolbar.py:83)
toolbar adapter /org/bluez/hci0 
_________
__init__ (/usr/lib/python3/dist-packages/blueman/main/Device.py:26)
caching initial properties 
_________
add_device (/usr/lib/python3/dist-packages/blueman/gui/DeviceList.py:317)
adding new device 
_________
do_cache (/usr/lib/python3/dist-packages/blueman/gui/DeviceList.py:496)
Caching new device C0:28:8D:81:64:5A 
_________
row_update_event (/usr/lib/python3/dist-packages/blueman/gui/manager/ManagerDeviceList.py:264)
row update event Fake False 
_________
row_update_event (/usr/lib/python3/dist-packages/blueman/gui/manager/ManagerDeviceList.py:264)
row update event Trusted 0 
_________
row_update_event (/usr/lib/python3/dist-packages/blueman/gui/manager/ManagerDeviceList.py:264)
row update event Paired 1 
_________
Generate (/usr/lib/python3/dist-packages/blueman/gui/manager/ManagerDeviceMenu.py:173)
UE BOOM 2 
_________
pa_context_event (/usr/lib/python3/dist-packages/blueman/main/PulseAudioUtils.py:341)
3 
_________
pa_context_event (/usr/lib/python3/dist-packages/blueman/main/PulseAudioUtils.py:341)
4 
_________
on_pa_ready (/usr/lib/python3/dist-packages/blueman/plugins/manager/PulseAudioProfile.py:29)
connected 
_________
<lambda> (/usr/lib/python3/dist-packages/blueman/main/PulseAudioUtils.py:353)
1 
_________
Generate (/usr/lib/python3/dist-packages/blueman/gui/manager/ManagerDeviceMenu.py:173)
UE BOOM 2 
_________
Generate (/usr/lib/python3/dist-packages/blueman/gui/manager/ManagerDeviceMenu.py:173)
UE BOOM 2 
_________
set_op (/usr/lib/python3/dist-packages/blueman/gui/manager/ManagerDeviceMenu.py:85)
op: regenerating instance <ManagerDeviceMenu.ManagerDeviceMenu object at 0x7f8fd0e05e10 (blueman+gui+manager+ManagerDeviceMenu+ManagerDeviceMenu at 0x1efcb60)> 
_________
set_op (/usr/lib/python3/dist-packages/blueman/gui/manager/ManagerDeviceMenu.py:85)
op: regenerating instance <ManagerDeviceMenu.ManagerDeviceMenu object at 0x7f8fd0e0eee8 (blueman+gui+manager+ManagerDeviceMenu+ManagerDeviceMenu at 0x1efce40)> 
_________
unset_op (/usr/lib/python3/dist-packages/blueman/gui/manager/ManagerDeviceMenu.py:99)
op: regenerating instance <ManagerDeviceMenu.ManagerDeviceMenu object at 0x7f8fd0e05e10 (blueman+gui+manager+ManagerDeviceMenu+ManagerDeviceMenu at 0x1efcb60)> 
_________
Generate (/usr/lib/python3/dist-packages/blueman/gui/manager/ManagerDeviceMenu.py:173)
UE BOOM 2 
_________
unset_op (/usr/lib/python3/dist-packages/blueman/gui/manager/ManagerDeviceMenu.py:99)
op: regenerating instance <ManagerDeviceMenu.ManagerDeviceMenu object at 0x7f8fd0e0eee8 (blueman+gui+manager+ManagerDeviceMenu+ManagerDeviceMenu at 0x1efce40)> 
_________
fail (/usr/lib/python3/dist-packages/blueman/gui/manager/ManagerDeviceMenu.py:124)
fail org.freedesktop.DBus.Python.blueman.bluez.errors.DBusFailedError: blueman.bluez.errors.DBusFailedError: Protocol not available

/usr/lib/python3/dist-packages/blueman/gui/manager/ManagerProgressbar.py:165: Warning: Source ID 697 was not found when attempting to remove it
  GObject.source_remove(self.gsource)

• But the problem is not the same as Bluetooth – Connection Failed: blueman.bluez.errors.DBusFailedError: Protocol Not available, because pulseaudio-module-bluetooth is already installed.

and

~$ pactl load-module module-bluetooth-discover
Failure: Module initialization failed

because it was already loaded.

Removing the device and trying to add it again: it is not found at all!

Which aspect in the normal operation of bluez – one that is available at system startup as well as by reinstalling the package – could be lost by restarting the session? – And how to avoid that loss?

UPDATE/EDIT by the OP:

[I am the OP. At some point I have deleted my account and then I came back with the same id.] I want to add that this is a Lubuntu-LXQt-specific problem. I have seen this problem in many Ubuntu and Ubuntu-based distros before 18.04, but in none since 18.x. Since 18.04 it is fixed excepting in Lubuntu-LXQt.

Details of the bluetooth adapter:

lsusb | grep Bluetooth
Bus 001 Device 013: ID 0489:e00f Foxconn / Hon Hai Foxconn T77H114 BCM2070 [Single-Chip Bluetooth 2.1 + EDR Adapter]