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Since upgrading to OS 15.1.1 my Time machine will get to about 80% then stop with the message "time machine could not complete backup because some files were unavailable. I've restarted with another drive as SU and run First Aid but same problem. From what I've seen here this is a bug in 15.1.1 and nothing can be done until Apple issues a fix. Or is there a workaround?
Mac mini (M1, 2020)
grantjeffries wrote:
Since upgrading to OS 15.1.1 my Time machine will get to about 80% then stop with the message "time machine could not complete backup because some files were unavailable. I've restarted with another drive as SU and run First Aid but same problem. From what I've seen here this is a bug in 15.1.1 and nothing can be done until Apple issues a fix. Or is there a workaround?
I am not familiar with a TM bug in 15.1.1
What I can say—
This is one of the classic error messages when a drive is working in a state of failure:
Time Machine has completed a new backup for you
can't create the backup
failed to complete the backup
an error occurred while preparing the backup
If you continue to get these errors I would suspect the Time Machine drive is starting to fail, the answer would be replace the drive and /or try another drive and compare your results..
Time Machine troubleshooting on Mac
Time Machine troubleshooting on Mac - Apple Support
If you value your user data
3-2-1 Backup Strategy: three copies of your data, two different methods, and one offsite.
More than one device, more than one backup methodology.
Another thing that comes to mind. Did you enable "sleep mode" on this Mac? This issue has come up with some folks with this mode enabled during an active TM backup.
That is: System Settings > Energy, and check the following two settings:
To prevent sleep, the first should enabled, and the second, disabled.
Lastly, the issue could also be due to files on the internal drive. Have you recently tried running Disk Utility's First Aid booted up in Recovery Mode on your Mac's internal drive?
If you're up to getting into the details of a Time Machine backup, I suggest you consider the following free app from The Eclectic Light Company: Time Machine Mechanic
It basically reads the macOS logs that pertain to the TM backup process so that you can get an idea where the process fails to complete. This could provide you with some clues on where to start troubleshooting. I do; however, concur with leroydouglas that the backup drive may be the culprit.
It isn't just you and likely not a drive failure. I'm having the same issue that started with 15.1.1. Basically it complains that it couldn't finish the backup because some files were not available and to try again when logged in. I think it has to do with the screen saver being active. If you don't let the screen saver start it should finish the backup. It happened in some minor release a few years ago and they eventually fixed it.
time machine could not complete backup
