Server Version#: 1.24.4.5081-e362dc1ee
Player Version#: 4.63.0
After optimizing the only selectable subtitles are the ones inside “Plex versions” folder, and plex ignores if you download any other subtitle. The only way to add a new subtitle is to enter the “other” version of the video and then from inside download and select it or add the subtitles before optimizing the video. If you optimize automatically the library this forces you to use the non optimized version or to delete and optimize everything again.