Samsung 49KS7000 transcodes AC3/DTS

Indeed, and sadly no idea why the ass was selected, since your subs are valid.

When said, this might be caused by:

But unsure here, and even more strange, that it works now, if nothing has changed?

If it happens again, we’ll need a small sample of the media:
https://support.plex.tv/articles/201035968-generating-sample-files-from-media/