Ubuntu 18.04 and bluetooth speaker JBL Charge 3

I upgraded to the new 18.04 version of ubuntu, coming from the latest 17. release. In both versions I have the same problem using my JBL Charge 3 bluetooth speaker. The sound is lagging and is being interrupted in uneven sequences, sometimes sounding OK for two seconds, then being interrupted in bursts.

I have tried disconnecting, re-connecting, switching HSP/HFP and A2DP Sink on and off, also "forgetting" the device and reconfiguring it.

My kernel (dmesg) says (repeatedly):

[ 5903.702600] input: FC:A8:9A:9B:81:E9 as /devices/virtual/input/input23
[ 5917.523365] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 5933.525358] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 5949.523345] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 5965.524317] Bluetooth: hci0: last event is not cmd complete (0x0f)
[ 5981.524464] Bluetooth: hci0: last event is not cmd complete (0x0f)

I have also tried this workaround without success.

The sound is distorted as long as the "bluetooth setting" windows is open and searching. Closing the windows clears the sound and stops the messages in the dmesg.

Blueman (alternative bluetooth manager) shows the same behavior while searching for devices, but the default bluetooth manager is constantly searching when open.

It would be interesting to discover if this affects only JBL speakers, and if it is a problem of some bluetooth controllers only (mine is a Intel 3165).