So I was correct the first time. It’s giving the successful 200 code and then kicks me out afterwards. It’s saying ‘Could Not Tune Channel’ only for some channels when the buffer is enabled with or without Xtream-Editor now. In rare instances getting a 408 error.
It sounds very similar to this with HDHomeRun:
Wonder if its just a current Plex bug then and nothing to do with Xteve? Without buffer works fine so I’m sticking with that for now.