Are you sure it’s 9.3 though? It hasn’t released for a lot of people including myself but if you go back a page or 2 there is a way to force it. I had unusable audio delay issues with surround sound (over arc) and looks like 9.3 has fixed it.
If you haven't done so already, try turning off volume leveling. Hit the * button while you are watching a show that's out of sync. Then you'll see the option for volume mode and you can turn it to OFF. That has worked for me and no sync issues since. I also only use the tv speakers. Good luck