Every so often (I'm not sure what causes it to happen), my phone removes all the personalized ringtones I've made and assigned to contacts. They are still in the music folder, but they are no longer assigned to anyone. This is also the case for notification tones. I'm using .mp3 files I created using Audacity on my computer that were added to the phone via USB. Is there any way to stop this from happening? Is it the software, or the type of files I'm using. Thanks in advance.