Call is not transferred to Sennheiser Bluetooth headset after auto-answer
I'm using a Sennheiser Presence bluetooth headset paired with my iPhone 5. After upgrading to iOS 8, auto-answer no longer works. Auto-answer is when the headset is paired but turned off, the phone rings, and the headset is turned on. It's supposed to answer the call, and transfer the call to the headset, but the last part doesn't happen. If I press the bluetooth icon on the iPhone (in the "call screen") it shows the call as being on the iPhone, and I can manually transfer the call to the headset, which works.
I've tried with a few other headsets we had lying around the office, and they all show the same behavior. This worked fine under iOS 7.x and earlier.
iPhone 5, iOS 8