I believe this post explained the problem better: Subtitles - 2 Brazilian Portuguese problems
Also, It’s important to report 3 bugs on the auto language selection for subtitles.
BUG 1:
Current behaviour:
Plex Server has three portuguese entries on the prefer subtitles dropdown menu: Português, Português (Brasil) and Português Brasileiro.
If you select Português Brasileiro and apply. Plex Server bugs and actually selects “Abkhazian”.
Expected behaviour:
After selecting “Português Brasileiro” from the dropdown menu. The server refreshes the media and auto selects Brazilian Portuguese subtitles.
BUG 2:
Current behaviour:
Plex Server has three portuguese entries on the prefer subtitles dropdown menu: Português, Português (Brasil) and Português Brasileiro.
If you select Português (Brasil), Plex seems to ignore this setting and picks the first available subtitle for a show (usually English).
Expected behaviour:
After selecting “Português (Brasil)” from the dropdown menu. The server refreshes the media and auto selects Brazilian Portuguese subtitles.
BUG 3:
Current behaviour:
Plex Server has three portuguese entries on the prefer subtitles dropdown menu: Português, Português (Brasil) and Português Brasileiro.
If you select Português, Plex seems indeed picks a portuguese subtitles from the available subtitles list, however, if there are two portuguese subtitles, it will always pick the first one, without checking if it’s meant for Portugal or Brazil.
Expected behaviour:
After selecting “Português” from the dropdown menu. The server refreshes the media and auto selects Portuguese, and not Brazilian Portuguese subtitles.