I had one problem that files without icons are not connected to the correct def files.
This depends on the descriptor settings, you have to set up recognition through by the acronym "MATCH" and no by extension.
All files even without icons will be recognized by Scalos FileType, Scalos "uses Def_Icons Wanderer/Workbench impostations, you can see it from my screnshot.
Scalos recognized and uses my def_Icons, others like for example the file "Enigma" which is MP3 is not well configured on "Scalos FileType", unfortunately you can't store it because "Scalos FileType" doesn't work and goes to Guru if you try to save !