OS X El Capitan had become something of a nightmare for many users, particularly of more recent models such as the last MacBook Pros and iMacs. Not only did OS X keep suffering kernel panics, manifesting as freezes requiring a forced or automatic restart, but its Bluetooth drivers were so easily blown away.

macOS Sierra 10.12 brought almost immediate relief from kernel panics, with a kernel that seemed to plod on doggedly no matter what you threw at it, but I’m afraid that it seems only to have ameliorated the problems with Bluetooth, not solved them.

Yesterday was a good example. My iMac17,1 still can’t go to sleep fully (it perhaps suffers from Ondine’s Curse), so I let it just sleep the display. We went out for what proved to be quite a bracing walk on the Downs, as we do, and on my return I tickled the Magic Trackpad 2 to bring it back to life. It had not actually put the display to sleep, but had gone into the screen saver. Stroking the trackpad did nothing, and the screen saver continued to run. I then tried tapping the trackpad down to the ‘tap’ point, only to discover that it felt dead, as if the Mac had panicked. I started to experience a distinct feeling of déjà vu, with memories of El Capitan’s problems flooding back.

I then pressed the Space bar on my Magic Keyboard, and the display jumped out of the screen saver. The trackpad remained lifeless, though, and the mouse pointer remained stuck firmly in the bottom left corner.

I keep a charged-up Magic Mouse 2 turned off but ready to use, by my iMac. Once that was turned on, it connected and I had regained control of the pointer. Miraculously (or about bloody time too, perhaps) the Magic Trackpad 2 started working again, and the iMac continued, as if nothing had been wrong.

Some other users, again I think MacBook Pro models are most likely to be affected, are still reporting occasional Bluetooth disconnects, which I also experience with my trackpad. They are nothing like as frequent as they were in El Capitan, and seem always to spontaneously reconnect. Incompatibility between Boot Camp and some recent MacBook models, reported in my list of bugs in 10.12.1, similarly seems to be the result of a Bluetooth driver issue.

I have also heard that users of some older Macs which Apple does not support for its Continuity features, including handoff, have reported issues. Some had upgraded their Macs with Bluetooth devices which fully support Bluetooth LE, and in El Capitan were able to use handoff as a result. When some such systems are upgraded to Sierra, they stop supporting Continuity, it appears.

The impression that I get is that, in El Capitan, the Bluetooth drivers in question could crash badly, and sometimes seemed to result in kernel panics. Sierra’s Bluetooth drivers are much more stable, but still flawed; although they do not seem able to cause panics (thankfully), there are still sufficient bugs to cause disconnects and other issues. In most cases, temporary problems can be rectified using another Bluetooth device, as I did to revive my trackpad.

Sierra’s Bluetooth problems are not as critical as those left in El Capitan, but hopefully they will be addressed in the 10.12.2 update, which is probably due this week or next.