if there is more than one subtitle for the language, use the first one

youtube_dl/extractor/youtube.py

@@ -493,6 +493,8 @@ def _get_available_subtitles(self, video_id, webpage):
         sub_lang_list = {}
         for l in lang_list:
             lang = l[1]
+            if lang in sub_lang_list:
+                continue
             params = compat_urllib_parse.urlencode({
                 'lang': lang,
                 'v': video_id,