it keep changing call and notification ringtones to "Unknown Ringtone",
I was using internal ringtones, not from sdcard.
When I go to settings to change the ringtone, mostly of times it show only ringtones from sdcard, it didn't show internal ringtones.
I already did try:
* clear data/cache of app com.android.providers.media
* deleted everything on sdcard
* clear dalvik cache
* factory reset, clear dalvik
* reflash Engle_Mars KitKat 4.4.2 2014-03-28
* reflash stock sbf than Engle_Mars KitKat 4.4.2 2014-03-28
none of them worked.