In Display and Monitor > Compositor, clicking on the Animation Speed slider makes it jump between minimum and maximum values.
Not sure if KWin uses Plasma QML components, or if this is a QtQuick bug.
Bug persists on Arch Linux running frameworks 5.49.
Can reproduce Distribution: KDE neon Developer Edition Kernel: 4.15.0-29-generic Plasma: 5.13.80 Apps: 18.11.70 Qt: 5.11.1 Frameworks: 5.50.0 Graphics: Card-1: Intel driver: i915 v: kernel bus ID: 00:02.0 chip ID: 8086:5917 Card-2: NVIDIA GM108M [GeForce 940MX] driver: nouveau v: kernel bus ID: 01:00.0 chip ID: 10de:134d Display: wayland server: X.Org 1.19.6 driver: modesetting,nouveau unloaded: fbdev,vesa alternate: nvidia compositor: kwin wayland resolution: 1920x1080~57Hz OpenGL: renderer: Mesa DRI Intel UHD Graphics 620 (Kabylake GT2) v: 4.5 Mesa 18.0.5 compat-v: 3.0 direct render: Yes
I also have this bug. Arch Linux KDE Plasma: 5.14.5 Qt: 5.12.0 KDE Frameworks: 5.54.0 5.0.0-rc2-mainline
I also have this bug. Operating System: Arch Linux KDE Plasma Version: 5.16.5 KDE Frameworks Version: 5.61.0 Qt Version: 5.13.0 Kernel Version: 5.2.11-arch1-1-ARCH
This slider has been removed in Plasma 5.18 and now lives in the General behavior page, where it does not have this problem.