When setting a specific ringtone, do not close that settings window. Look at the ringtone under the app settings and be sure it is shown there after changing it after backing out. If it is there, then back put again (don't close that window) from that window and it should take.
I agree as there is no indication that is a necessary step. There should be like an "Apply" function or something similar. This has worked like that for me since the S21 & 22. Please note that when I say this worked that way for me does not mean that is how it actually should function. This is the first time I have ever seen anyone bring this up before in these forums, so this could be a very rare bug.
Do you mean when you set a custom ringtone for a contact, it reverts to the default ringtone for the phone, or when you set the default ringtone for the phone, it reverts to the factory default?
Go to settings, sounds and vibration, ringtone, pick your ringtone. This will be the ringtone for general incoming calls that you have not set a custom ringtone for.
