1.3b3 no longer stops after a few seconds. Pausing and resuming are still fine.
I did some additional testing and it seems that changing sample rate is disturbing something. See log:
Opening track for playback: "x.wv"
[UPnP] Device protocol info:
[UPnP] http-get:*:audio/iLBC-sh:*,http-get:*:audio/midi:*,http-get:*:audio/mobile-xmf:*,http-get:*:audio/x-xmf:*,http-get:*:audio/mpeg:*,http-get:*:audio/qcelp:*,http-get:*:audio/riff-midi:*,http-get:*:audio/x-ac3:*,http-get:*:audio/x-amr-nb-sh:*,http-get:*:audio/x-amr-wb-sh:*,http-get:*:audio/x-celt:*,http-get:*:audio/x-flac:*,http-get:*:audio/flac:*,http-get:*:audio/x-gsm:*,http-get:*:audio/x-imelody:*,http-get:*:audio/x-m4a:*,http-get:*:audio/mp4:*,http-get:*:audio/x-musepack:*,http-get:*:audio/x-rf64:*,http-get:*:audio/x-speex:*,http-get:*:audio/x-ttafile:*,http-get:*:audio/x-vorbis:*,http-get:*:audio/x-vorbis+ogg:*,http-get:*:audio/x-wav:*,http-get:*:audio/mpeg:*,http-get:*:audio/x-aiff:*,http-get:*:audio/x-ay:*,http-get:*:audio/x-caf:*,http-get:*:audio/x-dts:*,http-get:*:audio/vnd.dts:*,http-get:*:audio/x-gbs:*,http-get:*:audio/x-gym:*,http-get:*:audio/x-ircam:*,http-get:*:audio/x-kss:*,http-get:*:audio/x-mod:*,http-get:*:audio/x-nist:*,http-get:*:audio/x-nsf:*,http-get:*:audio/x-paris:*,http-get:*:audio/x-sap:*,http-get:*:audio/x-sds:*,http-get:*:audio/x-shorten:*,http-get:*:audio/x-spc:*,http-get:*:audio/x-svx:*,http-get:*:audio/x-vgm:*,http-get:*:audio/x-voc:*,http-get:*:audio/x-w64:*,http-get:*:audio/x-wavpack:*,http-get:*:audio/x-wavpack-correction:*,http-get:*:audio/x-xi:*,http-get:*:audio/x-audible:*,http-get:*:audio/x-au:*,http-get:*:audio/x-sbc:*,http-get:*:audio/x-sid:*,http-get:*:audio/x-ms-wma:*
[UPnP] Listening on: 192.168.178.20
[UPnP] Stream address: http://192.168.178.20:63124/35/stream.wav
[UPnP] transport op: Play
[UPnP] transport op OK, took 0:00.032939
[UPnP] HTTP request #35: HTTP/1.1 GET /35/stream.wav
[UPnP] HTTP concurrency: 1
[UPnP] Source: 192.168.178.37:57924
[UPnP] Connection: close
[UPnP] Host: 192.168.178.20:63124
[UPnP] icy-metadata: 1
[UPnP] User-Agent: GStreamer souphttpsrc libsoup/2.56.1
[UPnP] Serving WAV
[UPnP] Accept-Ranges: none
[UPnP] Connection: close
[UPnP] Content-Type: audio/wav
[UPnP] Server: UPnP/1.0 DLNADOC/1.50, foobar2000/1.x
[UPnP] TransferMode.dlna.org: Streaming
[UPnP] Transport state: PLAYING
[UPnP] Transport state: PLAYING
[UPnP] Transport state: PLAYING
[UPnP] Transport state: PLAYING
[UPnP] Transport state: PLAYING
Opening track for playback: "y.wv"
[UPnP] HTTP request #35 finished
[UPnP] HTTP concurrency: 0
[UPnP] Device protocol info:
[UPnP] http-get:*:audio/iLBC-sh:*,http-get:*:audio/midi:*,http-get:*:audio/mobile-xmf:*,http-get:*:audio/x-xmf:*,http-get:*:audio/mpeg:*,http-get:*:audio/qcelp:*,http-get:*:audio/riff-midi:*,http-get:*:audio/x-ac3:*,http-get:*:audio/x-amr-nb-sh:*,http-get:*:audio/x-amr-wb-sh:*,http-get:*:audio/x-celt:*,http-get:*:audio/x-flac:*,http-get:*:audio/flac:*,http-get:*:audio/x-gsm:*,http-get:*:audio/x-imelody:*,http-get:*:audio/x-m4a:*,http-get:*:audio/mp4:*,http-get:*:audio/x-musepack:*,http-get:*:audio/x-rf64:*,http-get:*:audio/x-speex:*,http-get:*:audio/x-ttafile:*,http-get:*:audio/x-vorbis:*,http-get:*:audio/x-vorbis+ogg:*,http-get:*:audio/x-wav:*,http-get:*:audio/mpeg:*,http-get:*:audio/x-aiff:*,http-get:*:audio/x-ay:*,http-get:*:audio/x-caf:*,http-get:*:audio/x-dts:*,http-get:*:audio/vnd.dts:*,http-get:*:audio/x-gbs:*,http-get:*:audio/x-gym:*,http-get:*:audio/x-ircam:*,http-get:*:audio/x-kss:*,http-get:*:audio/x-mod:*,http-get:*:audio/x-nist:*,http-get:*:audio/x-nsf:*,http-get:*:audio/x-paris:*,http-get:*:audio/x-sap:*,http-get:*:audio/x-sds:*,http-get:*:audio/x-shorten:*,http-get:*:audio/x-spc:*,http-get:*:audio/x-svx:*,http-get:*:audio/x-vgm:*,http-get:*:audio/x-voc:*,http-get:*:audio/x-w64:*,http-get:*:audio/x-wavpack:*,http-get:*:audio/x-wavpack-correction:*,http-get:*:audio/x-xi:*,http-get:*:audio/x-audible:*,http-get:*:audio/x-au:*,http-get:*:audio/x-sbc:*,http-get:*:audio/x-sid:*,http-get:*:audio/x-ms-wma:*
[UPnP] Listening on: 192.168.178.20
[UPnP] Stream address: http://192.168.178.20:63124/36/stream.wav
[UPnP] transport op: Play
[UPnP] HTTP request #36: HTTP/1.1 GET /36/stream.wav
[UPnP] HTTP concurrency: 1
[UPnP] Source: 192.168.178.37:57936
[UPnP] Connection: close
[UPnP] Host: 192.168.178.20:63124
[UPnP] icy-metadata: 1
[UPnP] User-Agent: GStreamer souphttpsrc libsoup/2.56.1
[UPnP] Serving WAV
[UPnP] Accept-Ranges: none
[UPnP] Connection: close
[UPnP] Content-Type: audio/wav
[UPnP] Server: UPnP/1.0 DLNADOC/1.50, foobar2000/1.x
[UPnP] TransferMode.dlna.org: Streaming
[UPnP] transport op OK, took 0:00.054658
[UPnP] Transport state: TRANSITIONING
[UPnP] Transport state: TRANSITIONING
[UPnP] Transport state: TRANSITIONING
[UPnP] Transport state: TRANSITIONING
[UPnP] Transport state: TRANSITIONING
[UPnP] Transport state: TRANSITIONING
[UPnP] Transport state: TRANSITIONING
[UPnP] Transport state: TRANSITIONING
[UPnP] Transport state: TRANSITIONING
[UPnP] Transport state: TRANSITIONING
[UPnP] Transport state: TRANSITIONING
[UPnP] Transport state: TRANSITIONING
[UPnP] HTTP request #36 finished
[UPnP] HTTP concurrency: 0
Opening track for playback: "y.wv"
[UPnP] Device protocol info:
[UPnP] http-get:*:audio/iLBC-sh:*,http-get:*:audio/midi:*,http-get:*:audio/mobile-xmf:*,http-get:*:audio/x-xmf:*,http-get:*:audio/mpeg:*,http-get:*:audio/qcelp:*,http-get:*:audio/riff-midi:*,http-get:*:audio/x-ac3:*,http-get:*:audio/x-amr-nb-sh:*,http-get:*:audio/x-amr-wb-sh:*,http-get:*:audio/x-celt:*,http-get:*:audio/x-flac:*,http-get:*:audio/flac:*,http-get:*:audio/x-gsm:*,http-get:*:audio/x-imelody:*,http-get:*:audio/x-m4a:*,http-get:*:audio/mp4:*,http-get:*:audio/x-musepack:*,http-get:*:audio/x-rf64:*,http-get:*:audio/x-speex:*,http-get:*:audio/x-ttafile:*,http-get:*:audio/x-vorbis:*,http-get:*:audio/x-vorbis+ogg:*,http-get:*:audio/x-wav:*,http-get:*:audio/mpeg:*,http-get:*:audio/x-aiff:*,http-get:*:audio/x-ay:*,http-get:*:audio/x-caf:*,http-get:*:audio/x-dts:*,http-get:*:audio/vnd.dts:*,http-get:*:audio/x-gbs:*,http-get:*:audio/x-gym:*,http-get:*:audio/x-ircam:*,http-get:*:audio/x-kss:*,http-get:*:audio/x-mod:*,http-get:*:audio/x-nist:*,http-get:*:audio/x-nsf:*,http-get:*:audio/x-paris:*,http-get:*:audio/x-sap:*,http-get:*:audio/x-sds:*,http-get:*:audio/x-shorten:*,http-get:*:audio/x-spc:*,http-get:*:audio/x-svx:*,http-get:*:audio/x-vgm:*,http-get:*:audio/x-voc:*,http-get:*:audio/x-w64:*,http-get:*:audio/x-wavpack:*,http-get:*:audio/x-wavpack-correction:*,http-get:*:audio/x-xi:*,http-get:*:audio/x-audible:*,http-get:*:audio/x-au:*,http-get:*:audio/x-sbc:*,http-get:*:audio/x-sid:*,http-get:*:audio/x-ms-wma:*
[UPnP] Listening on: 192.168.178.20
[UPnP] Stream address: http://192.168.178.20:63124/37/stream.wav
[UPnP] transport op: Play
[UPnP] HTTP request #37: HTTP/1.1 GET /37/stream.wav
[UPnP] HTTP concurrency: 1
[UPnP] Source: 192.168.178.37:57944
[UPnP] Connection: close
[UPnP] Host: 192.168.178.20:63124
[UPnP] icy-metadata: 1
[UPnP] User-Agent: GStreamer souphttpsrc libsoup/2.56.1
[UPnP] Serving WAV
[UPnP] Accept-Ranges: none
[UPnP] Connection: close
[UPnP] Content-Type: audio/wav
[UPnP] Server: UPnP/1.0 DLNADOC/1.50, foobar2000/1.x
[UPnP] TransferMode.dlna.org: Streaming
[UPnP] transport op OK, took 0:00.082402
[UPnP] Transport state: PLAYING
[UPnP] Transport state: PLAYING
[UPnP] HTTP request #37 finished
[UPnP] HTTP concurrency: 0
File x.wv is 44.1kHz and file y.wv is 48kHz. (Both files are being down-sampled using the SOX re-sampler plug-in.) At first, playback for x.wv is started. Then after a while y.wv is being started. Then playback hangs with [UPnP] Transport state: TRANSITIONING, but after hitting Play again, it starts. This is not new for the beta. It happens with 1.2.1 too, using the same Raumfeld device.
Cheers.