I sent mine in as I had the same issue. They were unable to fix it. It is a known hardware issue. I have been issued a credit to order a new phone which I did. Hopefully whatever this issue is, they have worked out that bug in the new phones.
I had this problem. I had to send it in for repairs. They could not repair it. I was issued a credit to order a new phone. I haven't received it yet, but I hope they have fixed whatever this issue is for new phones.