To answer myself and to help someone else in this forum:
The problem was the bm2dx.dll PATCHED with "Enable Omnimix" option enabled.
Downloading the patched bm2dx.dll with that option DISABLED solved the problem. Don't care about d3d9 warning "W:graphics::d3d9: failed to acquire sub swap chain, hr=0x8876086c".
That's present even with the game perfectly running.