No SFX nor mechanical Sound (while music is OK)

[AlbertoZ70]

Hello, first post on this forum.

I just bought the pinball on Steam. Awesome simulation of a pinball.
While I get the music OK, there is no SFX nor mechanical sound on my Pro Pinball Ultra on Linux.
The Audio Sliders in "settings" work as above: Musci is OK, SFX and mechanical sound not ok, i.e. when I move sliders I don't get any sound (while I get in the "music" slider). Any suggestion on what to look at? Anyone else experiencing this issue?
I'm on Linux Mint 18.3.

Best regards,

Alberto