Some more info: After some (big) package updates the problem went away. vlc was updated, but libxcb1 and dragonplayer were not:
ii dragonplayer 4:15.08.2-1 ii libxcb1:amd64 1.11.1-1 ii vlc 2.2.1-5+b1 The breeze dependencies are now: ii breeze-cursor-theme 4:5.4.2-1 ii breeze-icon-theme 4:5.4.2-1 ii kde-style-breeze 4:5.4.2-1 ii kde-style-breeze-qt4 4:5.4.2-1 ii kwin-style-breeze 4:5.4.2-1 ii libc6:amd64 2.19-22 ii libkf5configcore5:amd64 5.15.0-1 ii libkf5coreaddons5:amd64 5.15.0-1 ii libkf5i18n5:amd64 5.15.0-1 ii libkf5kcmutils5:amd64 5.15.0-1 ii libqt5core5a:amd64 5.5.1+dfsg-6 ii libqt5gui5:amd64 5.5.1+dfsg-6 ii libqt5widgets5:amd64 5.5.1+dfsg-6 ii libstdc++6:amd64 5.2.1-23 ii qml-module-qtquick-controls-styles-breeze 4:5.4.2-1
