I feel the same. Yesterday I reassigned the same ringtone to this person & a bit later he called, in fact there were two calls from the same person & I was happy to see it rang correctly BOTH
times but today the same old trouble back to default ringtone. Now I have changed the default ringtone (as it came from the factory- ring ring) to another given by Samsung & should be in the phone memory (called 'Pure Tone'
), now I am waiting & watching