Why are my contacts uncustomizing the ringtones?

A minor problem, but an annoying one.

Occasionally there is need to reboot my Z30. After reboot, some, not all (and it seems to always be the same contacts) contacts become uncustomized and I have to reassign the ringtone to that contact.

Has anyone else had this problem?

I am running OS 10.2.1.2991 - Verizon has yet to release 10.3

Yes I had it in the past
Now that I have 10.3.1.1016 it's gone
But I have a different issue that sometimes it doesn't work at all let's say I silent a contact completely but it will still ring/vibrate I hope they'll fix it

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