Bubbleupnp sucks when I try to play the playlist. It plays only one track in the playlist and stops every time. I’m streaming to Volumio OS and it’s worked fine before. but after the latest updates Bubbleupnp no longer works. The music also chops wildly every time at the start of a song, no matter what song I play. It’s really boring 
The developer of Bubbleupnp claims that it is some code in Volumio OS that is old and therefore no longer compatible with Volumio OS. I am trying to stream Qobuz through Bubbleupnp to Raspberry Pi with latest Volumio OS. I have the same problem if I try to use the Mconnect app instead.
Volumio not compatible with Volumio sounds hard to do.
Sorry I mean between Bubbleupnp and Volumio OS 
I’ve been having exactly the same problem, in my case the source files being on MinimServer, running on another RPi (with Rasberry OS) and on the phone directly. Whether playing remote or local playlists to Volumio via BubbleUpnP, the music stops after one or two tracks. First I came to the conclusion the problem was with BubbleUpnP, as the same playlists proceed flawlessly when played directly using the Volumio app on my phone, rather than BubbleUpnP. However, I’ve just returned from a visit to my son for Christmas, and on his setup, which doesn’t involve Volumio, the playlists using BubbleUpnP to stream to his rendering devices also proceed without a hitch, so now I suspect Volumio as the culprit, especially after reading what you report the BubbleUpnP developer as saying, as Bubblesoft has been going for years and has a reputation as one one of the best and most reliable developers in the field. Time for the Volumio team to update their code!