Hi, just wanted to add to this that I experienced exactly the same behavior as the OP. One Sc5000 (connected to port 2 of the ethernet hub on the mixer if that makes any difference) happily playing beatport link tracks, and then randomly stopped playing everything.
What was interesting is that I was able to press the play/pause button to return it to a stopped state (despite it not actually playing anything), open the browser and load a new track, however, just as the OP stated, it would not actually play the track.
A restart of the deck resolved the issue, but it is concerning as I was part way through a set. Can also confirm the second deck was absolutely fine throughout, and the network was up and running fine.