Hi!
I'm not on a 950 (XL) .. I use a 930 and was on 10.0.10586.107 (or something like that). I had the same issues like crashing cortana etc.
I solved the problem by joining the insider program: NO fast, NO slow ring, BUT release preview!
Now I'm on 10.0.10586.338 and my Lumia 930 runs...