Sorry about my absence. As mentioned before in other threads, I was laboring through a sickness for last week and am just now back at the office. Here, we have already run a long-term test for BT but were not able to detect any errors or bugs.
We are now running another test with another speaker to see whether this might give us some more insight.
@antonio: please try temporarily deactivating the UPNP plugin for your LMS (Settings -> Plugins -> active Plugins -> remove tick -> save).
@muhackl: I just tested with a fresh install, could you try deactivating WiFi, rebooting and installing BT again?
@Stefan: thanks for helping out in my absence.
@hanoba: thank you for pointing out snapcast, might be worthwhile to look into for future updates.