Good evening Milincho,
On behalf of the team, my apologies for the trouble.
Some users report FxSound working fine with their surround setup, while others report problems.
This is just a (more-or-less educated) guess, but I’m guessing FxSound (and in particular the Surround effect) was created for 2.0 or 2.1 setups, and not with 5.1 and/or 7.1 setups in mind.
I’ve added your report to the existing thread on surround sound, which you can now find linked at the bottom of your post; so far, two solutions worth trying have been shared there by users who experienced similar issues:
Please let me know if these help.
I will also make sure to mention your report during the next team consultation.