When I try to raise or lower the volume on my laptop using Fn-F11 or Fn-12, the keypress "freezes", meaning that it continues to lower or raise the volume for up to 20 seconds.
The brightness keys (Fn-F5 and Fn-F6) work correctly.

Do you have any ideas ?

I'm using Leap with KDE Plasma 5, everything is up-to-date, the laptop is a Medion P-something.
Since the installation a few weeks ago it behaves like this, so it never worked correctly.