Some subs do not appear

I noticed some strange behavior with the subs while using Plex on my ATV thanks to PlexConnect:
When I select the sub on my ATV, sometime they do not appear when I watch the movie and if I do the same (same sub selection, same movie) on the Plex web app, the sub are appearing.
Any idea?

Thanks

I’m even facing some issues regarding the language, for example english is selected but the soundtrack played is in french. Again if I watch the movie on Plex web app no issue…
Overall it seems that the last release (PMS 1.1.4.2757 on macOS Sierra) I have more issues :confused:
Anyone in the position?