Please note the same issue described here: https://stackoverflow.com/questions/45847635/java-audio-clip-cannot-be-closed-when-using-linux-pulseaudio
The description contains simple Java code to reproduce the issue. The recommended work-around is to configure /etc/java-8-openjdk/sound.properties not to use Pulseaudio. I can confirm that the workaround works. So maybe Pulseaudio should not be the default setting in sound.properties.
