Yep, similar issues still with 11.1 and connectivity to Beats headphones (note, that's Beats, as in Beats as owned by Apple).
Both pairs of Beats I have (a Solo3 and Powerbeats) work perfectly with my MacBook. However on my iPhone 6, I get random disconnect/reconnect events, almost like the Bluetooth stack on the phone is crashing and restarting. This only started with 11.0
11.1 is a little bit better in that the disconnects don't happen as frequently but I still get them.
Apple have - clearly - fundamentally broken something related to Bluetooth in 11.x. regardless of whatever half-arsed excuses their support comes out with. It worked perfectly well in 10.x