restart your phone while pressing volume up, power button and Bixby buttons, release the power button when you seen the Samsung splash screen, once booted up release the Bixby and volume up button, on the menu go to clear cache, once complete select reboot phone. This should fix your issue, had the same happen to mine
Turn the Sound off then on, then reboot phone and check the ringtones.
You can also try the following:
Go to Settings -> Apps -> Show System Apps -> Ringtone Backup -> Storage -> Clear Cache
If issue persists, please send us an error report with screenshots from One UI Beta App (Beta Feedback -> Send feedback-> Error Reports -> "Select Category" -> Input frequency and Description" -> Send (Top Right Icon). We appreciate your help for supporting beta program.
