Not an answer to the OPs question, but when I saw your reply, I wondered, "Why would the OP reply to himself?" And then I realized you two are different users.
I should add - Try "German Audio Tech" out in Long Beach, CA. I've had success with him on my old BMWs (twice) and his repairs have been great for over 5+ years (I still speak to the current owners of my previous BMWs.) He should be able to tell you why it happens or what causes this.