It could be the sound device/audio driver or mp3 encoder on the server side or the media player. Since you had to restart ProScan to get it working normally, I would focus on the server side first. If it happens again, turn on the ProScan audio Loopback. If the audio repeats then perhaps it's the sound device or audio driver. Go to the Win Mixer Recorder tab and turn off any enhancements to see if that works. If the audio does not repeat then perhaps it's the mp3 encoder. In that case, I don't think anything can be done as something deep in the OS interrupted the mp3 encoding process. ProScan doesn't have a circular buffer. The audio from the OS API is sent directly to the mp3 encoder then it's sent out to the internet in near real time, about 200 to 300 milliseconds.
Also you may want to try restarting the media players rather than resetting the connection to Broadcastify. The reason is that the media player holds audio in the network buffer and will loop the audio if the connection goes down. Restarting the media player will empty the network buffer. Also some media players have a loop or repeat option so you may want to see if yours does and turn it off.