How to debug Bluetooth speaker/headset connection?

I am using a JBL Flip 3 Bluetooth speaker. The device works very well with my smartphone. I can also use it with my Ubuntu 16.04 laptop. However, the connection procedure is quite annoying. After some time I managed to find one process to get it to work:

0. Play music in Spotify. →sound comes from internal laptop speakers
1. Switch Bluetooth on
2. Select the speaker* toggle connection switch to "on"
3. Open sound settings
4. Select the Bluetooth speaker as sound sink, the mode is on "HiFi (A2DP)"
5. Play music in Spotify. →nothing to hear
6. Select "Headset Head Unit (HSP/HFP)". →sound comes from Bluetooth speaker in low quality
7. Toggle the speaker’s connection switch to "off"*
8. Toggle the speaker’s connection switch to "on"* →sound comes from Bluetooth speaker in low quality
9. Open sound settings
10. Select "HiFi (A2DP)". →sound comes from Bluetooth speaker in hifi quality

* Actions chosen from the Bluetooth icon in Ubuntu menu bar.

I have to repeat this procedure every time I want to connect the speaker. After every reboot, suspend or when the speaker shuts down for power saving.

My question: Where should I search for what is going wrong?

My approach so far was to look for messages in dmesg. I find some errors there:

[11967.266503] Bluetooth: hci0 SCO packet for unknown connection handle 0
[11967.716939] input: B8:69:C2:6C:7B:F1 as /devices/virtual/input/input19
[11972.471767] Bluetooth: hci0 SCO packet for unknown connection handle 257
[11972.471771] Bluetooth: hci0 SCO packet for unknown connection handle 257
[11972.471773] Bluetooth: hci0 SCO packet for unknown connection handle 257

But, I can not find anything helpful here.