Some sound effects are not always played (heard) via Q(SoundEffect) and Q(MediaPlayer).
Probably it depends on effect duration. I tried to change sample rate and bitness of the sample, but with no luck.

See attached simple example.
Steps to reproduce:
1. Run example
2. Click on "Play in loop" button - ok, we just checked that there is a sound and there's no problem with the sample itself.
3. Click on "Play once" button several times - sometimes (very often in my case) the sound is not heard at all.

Reproduced al least on Windows.
There was no such issue on Qt 5.15.2 so it looks as regression for new QtMultimedia in Qt 6.2.0.    see my comment below