Well, my recommendation would be bisection between 4.8.x stable commits. The stable kernel commits are plain and straightfoward without merges, so it's much easier for bisection. Linus' tree contains lots of merges, thus it's far more difficult to bisect. So, try the bisection of linux-stable.git tree. Try 4.8.6 and confirm that it works, then try 4.8.7 again and confirm it doesn't work. Then you can start bisection between 4.8.6 and 4.8.7.