I disabled the compression parameter from the import, because sometimes it tends to ruin sounds for some reason.
The GSThunder sound imports fine.
The GUI scroll sound somehow has a format that is not supported by Godot. When I open it in Audacity and re-export it, Godot is able to read it.
However, its sample rate is 192000 Hz instead of 44100 Hz, so when it gets imported it plays at a lower pitch.
The introdoors effect appears to import correctly, but when played I just hear half a second of white noise. Reexporting doesn't fix it.
I noticed the sound had a lot of saturation, so I normalized it and reexported again...
and Godot got stuck in an import loop with this error in the console:
ERROR: EditorNode::_sources_changed: Condition ' rimd.is_null() ' is true. Continuing..: At: tools\editor\editor_node.cpp:460
Looks awkwardly broken, but once the editor is restarted, the sound is there and plays correctly.
Looks like the audio import in Godot has a lot of progress to make... failing at importing WAV files is a bit lame :'D
This should be mentionned on Github with the files as an example.