Thanks for your explanation. It's interesting to see how very differently Bluez behaves on different phones. With the Nexus 5 (Bluez 4) no reconnect between calls would be required AFAIK. Then again, that's "academic" because the audio quality of those calls would be so bad making communication impossible (apparently an old Nexus 5 bug that was present under Android, too, when it was first released - Google managed to fix it with their first update - wish I knew how).

So, do I understand correctly that the bluetooth buttons issue is Jolla's problem because it's in the proprietary parts of SFOS?