A+ plays only one track in UPNP mode

Hi ,
I have the following problem with Audirvana in UPNP mode:
If I start an album (no matter if from Qobuz or my library…), Audirvana stops after the first track and I have to start the next song manually…again only one track and I have to start the 3rd song manually…
I only use the UPNP mode (to stream my music to an Astell&Kern Ak380 or a Naim Muso…Same issue with both)
No matter if I start the track directly from my MacMini or if I start from the remote App.
I completley deinstalled A+ and reinstalled but unfortunately same problem…
System: MacMini Late 2018, Mac OS 10.14.4

Thank you for your help!