Bluetooth headset: Pulseaudio cannot switch back from headset to HSP/HFP to A2DP

I have an Anker bluetooth headset which I would like to use for music and communication. Since Pulseaudio 10 supports to switch the profiles automatically, I was hoping to get a neat multimedia experience on Tumbleweed.

However, Pulseaudio swiches from A2DP to HSP/HFP, but not back.

Mai 22 17:11:51 mycomputer kernel: Bluetooth: hci0 SCO packet for unknown connection handle 0
Mai 22 17:11:51 mycomputer kernel: Bluetooth: hci0 SCO packet for unknown connection handle 0
Mai 22 17:11:51 mycomputer kernel: Bluetooth: hci0 SCO packet for unknown connection handle 0
Mai 22 17:11:51 mycomputer rtkit-daemon[2627]: Successfully made thread 7807 of process 2625 (/usr/bin/pulseaudio) owned by 'florian' RT at priority 5.
Mai 22 17:11:51 mycomputer rtkit-daemon[2627]: Supervising 6 threads of 1 processes of 1 users.
Mai 22 17:11:51 mycomputer kernel: Bluetooth: hci0 SCO packet for unknown connection handle 0
Mai 22 17:11:51 mycomputer kernel: Bluetooth: hci0 SCO packet for unknown connection handle 0
Mai 22 17:11:51 mycomputer kernel: Bluetooth: hci0 SCO packet for unknown connection handle 0
Mai 22 17:12:44 mycomputer pulseaudio[2625]: [pulseaudio] bluez5-util.c: Transport Acquire() failed for transport /org/bluez/hci0/dev_20_9B_A5_67_EF_C6/fd0 (Operation Not Authorized)
Mai 22 17:12:44 mycomputer pulseaudio[2625]: [pulseaudio] module-bluetooth-policy.c: Could not set profile 'a2dp_sink'
Mai 22 17:12:45 mycomputer kernel: Bluetooth: hci0 SCO packet for unknown connection handle 257
Mai 22 17:12:45 mycomputer kernel: Bluetooth: hci0 SCO packet for unknown connection handle 257
Mai 22 17:13:09 mycomputer pulseaudio[2625]: [pulseaudio] bluez5-util.c: Transport Acquire() failed for transport /org/bluez/hci0/dev_20_9B_A5_67_EF_C6/fd0 (Operation Not Authorized)

Can someone give me a hint how to debug this properly?

Thanks,
Florian

This is just a wild guess but maybe try this with some modifications? (the files may be in different places on Ubuntu):

https://bugs.launchpad.net/ubuntu/+source/bluez/+bug/1438510/comments/5

Or you might also want to go through this bug report:
https://bugs.launchpad.net/ubuntu/+source/pulseaudio/+bug/1582213