I'm using v3.0.2 on a Windows 10 computer. This configuration was working fine until just the past few weeks.
Clicking the Play button to start an mp4 drops the Widows Mixer fader for VLC media player (LibVLC 3.0.18) to zero. The OpenLP-(service name) fader next to it stays up. Bringing the level up restores the audio, but clicking the Play button for the next video kills it again.