I’ve done the cables, kezo but haven’t got round to doing your tests.
If you get 5 tomorrow put a pic up of TV sound settings.
In the meantime you could also contact Hisense support by phone or better email explaining the problem. There likely to send a shiny new USB stick with firmware or software on to fix the bug, albeit after a bit of toing and froing. Or we will do a work around 🙂
Ive also read your AV manual.