I don't have this problem with two other iPhones. And previous to my screwing around, it'd work flawlessly since a bought it (launch day.)
Could I have screwed up a mixrate setting someplace? I do have a custom mixer xml for boosting headphone port and speaker audio but I never touched the settings for the bluetooth driver.
This behavior is intermittent and it matters very little what content I'm playing through it. I do notice that when this is happening, no metadata or control is capable through AVRCP either. (i.e. Pandora app can't connect to the phone, no album art, etc)
Sometimes it'll stop doing it and play normally for the rest of the session (drive) after a few minutes and everything is normal. Sometimes it doesn't do it at all and sometimes I can't get it work normally at all.
Here's a video showing the behavior: