I've Freepbx13 and Asterisk 13. Uptodate modules.
My default langue is French in Sound Language Module.
I put some system recordings that I use for annoncements. I put the System recording in French language (to match with my default language setting).
But when I've in use the system recording in a ring group or an IVR, Asterisk read the file in english format :
Playing 'custom/repondeur.slin' (language 'en')