OS X 10.11.6 has been publicly available for just a few days, but the unfixed bugs are already making themselves only too apparent; here is a list of its bugs of which I am aware.
Sporadic freezing, requiring a forced or automatic restart
Some models, notably MacBook Pro Retina, 13″, Early 2015 (MacBookPro12,1) and possibly iMac Retina 5K, 27″, Late 2015 (iMac17,1), freeze periodically when running 10.11.4 or 10.11.5, and will either restart automatically, or if that fails they require a forced restart. This has still not been fixed in 10.11.6, although on this iMac17,1 it as about half as frequent as before.
Bluetooth, Magic Trackpad 2 – sporadic loss of connection with Apple Magic Trackpad 2
Occasionally, and infrequently, a Magic Trackpad 2 will become unresponsive, and warning that it has become disconnected will be shown on screen. I have not yet experienced this in 10.11.6, but others have, so it still seems to occur.
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, and listed it as present in 10.11.2 to 10.11.5. The only workaround is to select a different folder, then to select the correct folder again.
Core Foundation library – loss of drag and drop
After a certain period working in El Capitan, 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).
The frequency of this occurring had been diminishing with 10.11.3 to 10.11.5, but seems to have been more troublesome again in 10.11.6. It has definitely not been fixed yet.
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 remain in 10.11.6 just as in 10.11.2 to 10.11.5.
The only workaround is to use a third-party tool such as MacPilot to edit the preferences instead of the bundled pane.
Power Management – hard drives always put to sleep on system sleep
On some recent iMacs at least, Power Management ignores any setting to not put hard drives to sleep: when system sleep occurs, the hard drive in an internal Fusion Drive is always put to sleep, regardless of the drive sleep setting. This is detailed here, and has been present in 10.11.4 and 10.11.6.
The only workaround is to set the system sleep time to Never, which also stops hard drives from being put to sleep.
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 persists in 10.11.6.
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 10.11.6.
There is no workaround.
Preview 8.1 – cannot work with high resolution images
Images of resolutions around 53671 x 47584 pixels will open in Preview, but attempting to zoom or move around results in breakup of the image within the window, and display of junk image fragments. This appears specific to Preview and does not affect third-party app like GraphicConverter. It may be specific to certain graphics cards or drivers. This is detailed here.
The workaround is to open the images using another app, such as GraphicConverter.
Disk Utility – inability to change partition size of some disks
This old bug, which used to result in an error reported as “partition (map) too small”, was eliminated in 10.11.5: Disk Utility then refused to select disks for which it could not change the partition size. I do not know whether this has changed in 10.11.6.
Loss of USB audio output – sporadic loss of connection to USB audio output devices
Some users report that audio output devices attached via USB will spontaneously disconnect, with audio output reverting to internal speakers. This appears to relate to a bug in the USB audio output driver, and I do not yet know whether this has been fixed in 10.11.6.
Please add your own experiences and I will incorporate as necessary…
(Updated 31 July 2016)