Notification Sounds (volume change, Spectacle shutter) disappear when changing their volume in Sound KCM, and the volume slider starts to work incorrectly.
STEPS TO REPRODUCE
1. Go to sound settings, apps.
2. To try to change the volume level of your notifications.
The inability to change the volume of notifications and complete disappearance of their sounds.
openSUSE Tumbleweed and KDE Neon User Edition with KDE Plasma 5.17.2
*** This bug has been marked as a duplicate of bug 407397 ***