I've assigned a default ringtone and one other ringtone to my wife. She called me two days ago and the phone played the Galaxy SII ringtone. Next day, somebody else called me, and the same happened.
So, I assigned the ringtones again, but I was wondering if this happens often, does it happen to others, is there a reason it happened to me (did I do something wrong)...
Probably it's a bug. Last night, the OS updated itself, and the ringtones were not affected.