Windows Mixer level goes to 0 when Play button clicked

FMA_CR

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.

FMA_CR

Turned out to be just operator error. The (unlabeled) audio level slider next to the media playback progress bar was set to no output. Apparently it acts as a preset level for the Windows Mixer's VLC fader that is reset with every Play command. Someone must have reset the slider by accident.
Now, we know!