I have thousands of subtitles downloaded by Subzero (plugin for Plex) and Bazarr in Brazilian Portuguese. These two software add “pt-BR” at the end of the file to differentiate it from “pt” which is Portuguese from Portugal. Infuse is labeling these subtitles as “Breton”, perhaps because it is just reading “BR”.
Are you streaming these files from Plex? Are the subtitles visible there?
The error continues. Subtitles with the ending “pt-BR” (Brazilian Portuguese) are identified as Breton.