The instrument Unreal Standard Guitar is reported as non working. @st3r4g
https://unreal-instruments.wixsite.com/unreal-instruments/standard-guitar

The reason appears to be: the instrument contains multiple <global> headers.
These globals have different values for sw_default.
Apparently, sfizz should handle sw_default independently for each of these globals.
Currently one applies for the entire system.

There might be other problems as well. @st3r4g has provided a patch that permits to get sound out of the instrument.
https://gist.github.com/st3r4g/fa238f72bd49a171933499cd86536289