correct. that means the official platform restrictions apply which can be particularly tricky with HEVC that’s not Apple compliant.
Could be some deviation from how Apple likes its HEVC encoded or something about the combination of streams in your file.
Why not using the new player.
I suppose it’s safe to assume the old one will be going away at some point… so if there’s some files/situations where you run into issues with that, it might be worth addressing them.