I really don't know where the ringer issue is coming from. I just went back to 4.5 and built a ROM using that without adding/removing anythings from the kitchen (so 21028 sys), and I still am getting the no ring (but will vibrate) on incoming calls. This is certainly a weird (and widespread) problem, but I like flashing my phone anyway. It's felt weird not flashing for a few days
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