Hopefully this might help someone:
Same issue on the ps5.
Playing in two player local co-op. Final cutscene no sound, so we quit to try and get out before it ends the scene so we could try and watch it again but when we reloaded we were in front of the completed tiara but we didn’t have the end items or couldn’t watch the end cut scene.
My solution. PS5 FIX. ISH…
After this issue, and before quitting the game I jumped into the ps5 menu and downloaded the cloud save to the console. This was older than the current save as it was from the last play session. we only lost about half an hour’s worth of stuff.
Reloaded. Replayed the bit we had just done. Then as a precaution, just before we got ok the chariot we quit the game and backed the new local save to the cloud.
Also this time just before breaking the kidney stone we took another precaution and the 2nd player left, so it was in solo mode This time cut scene worked, and we got the items and trophy.
So probably not gonna help everyone, but as a precaution - back up your save before chariot if you can. If it’s too late,.check the date on your cloud save file. Unsure when it backs things up, maybe over night? You might just catch it on time!
Sorry, I know this won’t help everyone. Hopefully it will help some though, until Devs can fix.