I'm having the same problem when connecting a pair of Philips SHB5950 headphones to the integrated Bluetooth controller of a Dell XPS 15 9550 (BIOS version 01.00.07).
Upstream kernels 4.6.x, 4.7.x and 4.8.x all give the same problem: the headphones pair and work fine in HSP mode, but will not switch to A2DP mode.
I'm having the same problem when connecting a pair of Philips SHB5950 headphones to the integrated Bluetooth controller of a Dell XPS 15 9550 (BIOS version 01.00.07).
Upstream kernels 4.6.x, 4.7.x and 4.8.x all give the same problem: the headphones pair and work fine in HSP mode, but will not switch to A2DP mode.