On Apple TV: The enhanced player was not enabled, because it was causing a/v sync issues. I turned it back on, and at least now the ATV no longer crashes.
On Mac: I discovered that PMP has been discontinued and replaced with “Plex”. This seems to partially fix the subtitles bug - turning subtitles off causes an error. But if you then re-open the live TV channel, the subtitles are now off, even through the UI shows them to still be on.
So, lots of issues still, but at least new workarounds.
Similar issue. Not live TV but downloaded media. On iOS, no subtitles. On AppleTV. subtitles, despite “none” being selected in the drop down for subtitles.