Hello.

I tried to write about this long time ago, but capcha didn't let me in to bugtracker.
I also tried to connect by email, I even received answer, but something goed wrong.
This bug completely tired and ruined my nerves. I cannot work while it's present.

There is enought major bug in sfz engine.

It's present when you work with .sfz files, where there are two different groups 
(which are activated by the same key (for example, C4); first group is activated by key pressing, second - releasing; first group is deactivated by activating second group, second - first group).

Sounds of samples from this groups are not muted after event, which was specified to mute this sounds.

Example .sfz file: http://pastebin.com/Qb8KUusQ
From there you can see definitions of such two groups:
<group> loop_mode=no_loop sw_lokey=B0 sw_hikey=B0 sw_last=B0 group=1 off_by=2 trigger=attack
, and
<group> loop_mode=one_shot sw_lokey=B0 sw_hikey=B0 sw_last=B0 group=2 off_by=1 trigger=release
.

This bug can be met, for example, when you're using or making string tremolo instruments (where sounds of stroke up and stroke down differ).

Best regards,
Vladislav