Suddenly can't play 4k content

[skribe]

This stream is being transcoded because of what appears to be audio and video formats unsupported by the client device. Without hardware acceleration, your server simply cannot keep up with a 4K transcode. Your ffmpeg logs show that you're getting 10-13 fps, but a movie is approximately 23 fps. So the transcode is not fast enough to support the stream.

I'm afraid your best option here is to do the work to enable hardware acceleration.

If it worked before, I'm not sure why. Your client is telling the server that it doesn't support these encodings.