I do encounter the same issues as reported above (audio cant be reproduced on reconnect or is routed through phone speaker).
Restarting bluetooth semi-consistently restores functionality. I sometimes restart the audio subsystem too just to be sure.
This is occasionally not enough and even Media Player needs to be reopened.
Interestingly, those issues happen with my valco vmk 25.2, but not with some older Sennheiser hd 4.50.
The only difference i can spot is the bluetooth protocol being 5.4 for the valco and 4.0 for the sennheiser.
Would you like some more debugging data or the mentioned fixes cover this?
Are the steps mentioned here still relevant by the way Collect Bluetooth Logs | Sailfish OS Documentation
Edit: potentially the AAS BT bridge logs are more Interesting to collect, as mentioned here AppSupport Bluetooth feedback thread