I suspect this is a general iOS issue. BT on my phone has been routinely crashing and restarting for at least six months, long before iOS 10. I thought it was the connected device, but then I saw it with multiple devices connected and all lost the phone at the same time, and a minute or two later, they all reconnected. I have upgraded both iOS and phone, and the problem persists. If I were going to guess, there is a software defect in Apple's BT stack in iOS.