My guess is that it is caused by a bandwith bottleneck on your LAN when the client starts the download of the track from the server. How fast is your LAN? If you are on wifi, then try using an Ethernet connection instead...
The two wired segments are running at 1 Gb/s and 100 Mb/s, respectively, with very little traffic (basically just an active iPad with JRemote talking back to MC and the DLNA receiver). The wireless segment is running 802.11n; the receiver is running on the wired segment "after" the wireless bridge. A Roku (also wired on that same segment) is able to stream HD movies in 5.1 from Vudu without issue. Using an Airport Express (with this and the previous receiver), playback has also been fine for years.
My first inclination is to think that there's plenty of BW (and responsiveness) for a 16-bit stereo PCM stream.
Disabling SetNext also definitely had an impact (seemingly eliminating the problem). I would like to have gapless playback, so thus my various experiments with SetNext re-enabled. I'm willing to buy into the notion that there is something about the communication between the receiver and JRiver that, only eventually, confuses the receiver. That seems to be the case since SetNext functionality
does appear to work (it's advertised as implemented and does achieve gapless playback when enabled). I am thoroughly confused why the problem takes a while to manifest, which lends some credence to suspecting network traffic. It's just hard to believe that the fairly limited communication I've seen for DLNA would stress the network.
I would like to understand the protocol involved in push playlist changes over DLNA better. Does the DLNA Control Point first pause or stop the renderer, push the new media URIs, and then "push" play?