I recently updated to KDE 5.8 and I have this weird and irritating behavior: if I turn the sound off, either as "mute" or lowering to 0, and a window starts playing sound (for example youtube), the volume automatically goes up.

How can I fix that?

Thanks

Kubuntu 16.04, plasma 5.8.5, kde framework 5.28.0, QT 5.6.1