After an upgrade from 4.7.4 to 4.8.0, the single-click popup slider has the maximal volume on the left while minimal volume on the right. I'm in the Czech Republic, using the English language for KDE (with Czech KDE-based locales, but English as a language), so I naturally expect to have minimal volume on the left hand side and maximal volume on the right hand side. I don't care whether the slider is vertical or horizontal, but I certainly don't want to have zero on the right or at the top, sorry. Also, the about dialog says "kmix 4.8.0", but bugzilla contains just "4" as the version, so I'm filing that as unspecified.
The 4.9.0 version has the scrollbar in the sane orientation again, closing.