kde upgrade, reboot, bad sound, reboot, good sound

Hello! While it is not really an issue, I wonder why this is occuring in this way... Some days ago, an update of KDE was available. I installed it with apt. After the first reboot following that install, the sound generated was really bad (a bit as if some frequencies were taken away and it had to make its way through vocal chords (vibrating sound)). Since this had occured before, I knew I had to reboot a second time to get the sound working well again without a single issue. Why is that? Is it because I installed some components that were in use? If so, why does it need two reboots to get it working? Thanks for the info! Patrick