There is new issue related to FL sound:

I noticed, that adjusting volume using side volume keys do not work, when Flash Lite is launched
as Symbian application (SIS) using standard stub library.

( See: )

BUT, when stub is not used (possible for old 3.0 devices), it works.
In new devices stub must be used, because sandboxing issues, so the bug will exist there.
Also when SWF is launched from native player, there are no issues.

I stronly believe, its due some missing capabilities (MultimediaDD perhaps), like with this bug:,_FP1

There is no solution, due fact it is not possible to add those ultra sensitive capabilities.

If you like to check this out, you can use KuneriLite to enable/disable stub and
install any SWF with sound.