STEPS TO REPRODUCE
1.Check the repeat of the sound file
The second and subsequent playbacks will be the volume of the system sound.
Set the changed volume for the second and subsequent playbacks
KAlarm Version 3.3.6 (KDE Apps 21.12.3)
This has now been fixed by commit 45f4df183ebaf94bbdf42652d8fc843056e26abe for KAlarm version 2.5.0, which will be released in KDE Gear 22.08.
Thank you for reporting this bug!