Note that bad features, poor interface design, and problems with third-party apps, etc., are listed separately here.
Following the release of Sierra 10.12.6, this list has been superseded by the new list for 10.12.6. This list is no longer maintained: please refer to that last for the latest information.
If you are looking for a list of bugs in previous versions of Sierra, that for 10.12.4 is here, for 10.12.3 is here, for 10.12.2 is here, for 10.12.1 is here and for 10.12 is here. Note, though, that those are no longer maintained.
Boot Camp – broken on recent MacBook models
Although Boot Camp seems to have been working fine for almost all Sierra users with 10.12.0, the update to 10.12.1 appears to have broken it on some recent MacBook models, particular Retina versions. There is long and agonised discussion about this here, but it seems to be the result of new Bluetooth drivers which came with the 10.12.1 updated. If you’re affected, the only solution at the moment seems to be to roll back to 10.12.0.
About This Mac / Storage never completes
If you open About This Mac and select the Storage tab, the top bar should, after a while, display the disk usage on your startup volume. Many users report that this remains stuck at Calculating…, and that one or more of the sections in the left of the Manage… dialog also remain busy and never report a size, even after 2 weeks. These appear to be bugs, and have been present since 10.12. No workaround has been discovered.
Console – no access to full historic log data
The Console utility does not provide full access to log entries already gathered before the app is opened.
Workaround: use the
log show command in Terminal, or LogLogger5a from here.
log (command) – bugs in
collect options (improved but not yet fixed)
log show, the
--end options now work better, but still do not discover all log entries in the specified time period. Widening the time window will normally result in discovering more entries in any given period.
Workaround: widen the time window specified by
--end, or use
log collect --size option still does not restrict the size of log entries output – it is functionless and there is no workaround.
Recovery mode – may require a wired USB keyboard to enter
Prior to macOS Sierra, it was usually possible to enter Recovery mode, holding the Command and R keys during startup, using a wireless keyboard. Trying to do the same in Sierra 10.12.1 may fail, and normal startup proceeds.
Workaround: use a wired (USB) keyboard, or connect an Apple Magic Keyboard using its charging cable.
Finder aliases shown as documents
There is an intermittent bug in Sierra’s Finder which sometimes shows some aliases with the generic document icon. It should not affect their function as aliases (although it can sometimes confuse File Open and Save dialogs), so this appears cosmetic if irritating. This has been present since 10.12, and additional details are here.
Finder – incorrect column width
This can occur when using Finder windows which are set to column view. When switching folder in the view, the rightmost column being displayed has excessive width, filling the Finder window, its divider being placed incorrectly at the right edge of that window.
This long-standing but intermittent bug dates back to Mavericks if not earlier, and I have whinged about it here and here. It was also present in every version of El Capitan. The only workaround is to select a different folder, then to select the correct folder again.
Finder – inconsistencies and other bugs in List views
There are several bugs in the Finder’s handling of maximize (zoom), which are most prominent, and perhaps largely confined to, List views. The most obvious, reported here, is that maximising List views often doesn’t result in a window which is deep enough to contain all the items in the view, even though there is ample space to do so. Various other issues have been reported – see the comments to this article for fuller details.
Although these don’t have major impact, and can be worked around, they are messy and inconsistent.
Core Foundation library – loss of drag and drop
After a certain period working in Sierra, attempts to drag and drop or otherwise cut/copy and paste content fail with a Core Foundation error. In the case of drag and drop, this is likely to be the result of a memory leak, or similar. I have discussed this issue here. Once it occurs, the only way to restore normal function seems to be to log off and log back on again (or restart).
This bug first appeared in El Capitan, and now appears less frequently in Sierra, but can still occur.
Energy Saver pane – inconsistencies in controls
The features available in the Energy Saver pane of System Preferences are inconsistent between Macs, and incomplete, for example not providing a separate control slider for system sleep on some hardware. Further details are here. These are unchanged in Sierra 10.12 and 10.12.1.
App Store – dysfunctional behaviour
There are many issues with the App Store app and service which are usually worst when there are several major updates to Apple software. These range from update errors and non-availability to failure to list updates in the Updates pane if there are more than about seven updates pending. At their worst, behaviour becomes completely unpredictable, and updates fail, sometimes requiring the whole app to be downloaded again. I have detailed these, and a partial solution to some which can be used from the command line, in this article.
There is no workaround, of course.
Time Machine – failed backup following a forced shutdown
Sometimes, if a Mac has had to be shut down forcibly, on starting up again Time Machine backups fail. There are two solutions: unmount and then remount the backup volume, or if that does not fix the problem, restart. If the problem persists after a restart, use Disk Utility to perform First Aid on the backup volume.
There are many who have experienced problems with Time Machine since upgrading to Sierra. Whilst there may be underlying bugs in Time Machine, many if not most problems can be resolved by following suggestions here. If those do not work, contact Apple support so that Apple is aware of the issue. Remember that some anti-virus products can cause severe problems with Time Machine, and may need to be disabled.
Keychains – repeatedly having to enter the password to unlock
Some users are apparently suffering from repeated prompts to enter their keychain password, in order to unlock it, despite having their keychain set to be left unlocked. There appear to be bugs causing this, but some problems may be solved by following advice in this article. If those do not solve your problem, please call Apple support so that they are aware of the issue.
Bluetooth – spontaneous disconnections and others
Although much improved from El Capitan, there are still problems which appear attributable to bugs in Bluetooth drivers. These include spontaneous disconnection of connected devices such as the Magic Trackpad 2, loss of Continuity features on some models, and the incompatibility with Boot Camp of some recent MacBooks noted above. These are generally infrequent, and very unlikely to result in kernel panics (unless those in El Capitan). Further details are here.
OS X internals – clicking on a window causes it to jump
When switching between apps by clicking on a window, sometimes the selected app comes to the front and its window jumps to a new position on screen. I used to think that this was confined to certain apps such as Tweetbot, but it also affects Apple’s Messages app and others, and has persisted through El Capitan into Sierra 10.12.1.
The workaround is to switch to that other app by clicking on its icon in the Dock.
Trackpad – unexpected shift of text insertion point
This is another long-standing bug, which goes back to the early days of Apple’s Magic Trackpad in about 2010. You are typing along happily, with your hands well clear of the trackpad, and suddenly the text insertion point jumps to a different location in the text which you are editing. This is sporadic and completely unpredictable, but affects a wide range of different apps, and still affects 10.12.1.
There is no workaround.
Apple Magic Keyboard – duplicated letters
Sometimes, when typing normally, letters are incorrectly duplicated although if the key had been held pressed for too long, that would not have resulted in keystroke repeat, but would have popped up the accented character picker. This has been a sporadic problem since El Capitan but seems to have become more noticeable in Sierra.
I suspect the workaround is to use a wired keyboard.
Disk Utility’s First Aid – fails when run on SoftRAID RAIDsets
If you try running the First Aid feature in Disk Utility on a RAID array being driven by SoftRAID, the process is likely to fail. SoftRAID details a workaround using the command line in Terminal.
System Integrity Protection (SIP) – zero-day vulnerability
There is a zero-day vulnerability in El Capitan’s and Sierra’s SIP which could be locally exploited. Further information is here, and full details here.
As this cannot (yet) be exploited remotely, users should be wary of this potential for local attack.
Finder and file system (HFS+) – strange behaviours with ~/Library/Mobile Documents
The ‘folder’ ~/Library/Mobile Documents cannot be opened in the Finder, but redirects to iCloudDrive. The odd behaviours associated with this are detailed here, and are not bugs but ‘features’. The workaround is to access them via Terminal, as detailed in that article.
Please add your own experiences and I will incorporate as necessary…
(Updated 15 December 2016)