Time Machine backup on macOS Sequoia cannot be completed

I resolved the issue after working with an Apple support person. I have an MBP M1 Pro with MacOS 15.1.1. and I had failures with TM both on NAS and hard wired backups. My workaround, as per the boards, was to to turn off the MacOS Firewall to let the backups work to completion.

However, I also have a cyber security software which includes a firewall of its own. There is a conflict between its firewall and the MacOS one starting with Sequoia 15.x. After I turned off the security software firewall and left the Mac OS one active, all TM backups work without error. The 3rd party cyber security software firewalls need to be updated for Sequoia.

I found a solution for us for the same problem:

we have 2x users installed on our iMac: both with admin rights.

After each OS version update, TM was unable to complete the backup for the respective registered user.

Switching to the other user and restarting the backup there --> everything was OK.

Back to the first user --> then no more problem, the backup runs through.

So the problem obviously seems to have been a rights problem.

All backups are also made twice on different storage devices:

1x on an Unraid server (NAS) as an smb-share

1x to an external drive connected directly to the iMac (AFPS)

Initially, the backup didn't work for either of them. After the switch, the backup worked again for both of them.

So in this case it has nothing to do with the type of connection.

Hope it helps ...

When you do a Command I (Get Info) on the History.db file in /Users/your user account/Library/Safari/History.db do you see your User Account listed under Name and Privilege mine was missing when I went from Intel to M4 PRO I added it in and it solved my problem.

@NightSailor I tried that and I had no luck.

So I bit the bullet and bought a new external drive, attached it to my MBAir and set up a new Time Machine. It immediately reformatted it to the new format and went off and succesfully completed a new backup and it's working fine now.

As far as I can see, the issue for me was simply the format of the drive. Since Apple changed their Time Machine Backup standard to a format of APFS anything that is formatted in a legacy format is unsupported. That is pretty lame of Apple as for me it renders years of Time Machine backup data practically useless unless I go and access the old external drive from a MacBook that is still on a version of MacOS that supports the legacy format. Apple should have created a pathway to convert the backup data from the legacy format to the new format.

All of these posts about deleting the default nsmb.conf file are completely irrelevant as backups fail whether backing up to a remote drive over SMB or over a local drive.

The problem is happening because Time Machine is being refused access to certain locked files. The specific files can be viewed by searching the logs for the last 24 hours or so:

log show --info --style compact --predicate '(subsystem == "com.apple.TimeMachine")' --last 24h

Time Machine should have full disk access so this is a bug in MacOS.

Yes - the problem is very much related to Time Machine losing permissions to certain files when the machine sleeps. I've worked around this (until it's fixed) by making the following changes to power management:

sudo pmset -b hibernatemode 0

sudo pmset -b standby 0

sudo pmset -b disksleep 1

What this does is prevent the machine from fully hibernating. This will affect battery life a little if it's a laptop you regularly take about the place, but in general terms this is how MacOS -used- to operate.

I've been running Time Machine on my Synology NAS. It worked for many years, but after Sequoia I had a lot of problems - backups kept disappearing, issues with failure to back-up etc. One notable problem is the current process where backups are deferred when in lock screen, and are supposed to resume when unlocked; sometimes they don't. I have tried a disconnect and re-connect, and the system check is good but then the backup fails; an erase and new backup just ends up with the same problems. I did discover that some files won't back up to a NAS (Garage Band files, for example).

I have always used Bombich CCC (Carbon Copy Cloner) for other backup tasks, and I've now switched to that for backup to NAS - works perfectly. It has far better functionality, has snapshots, and good file filters; it also has excellent technical support, whereas apple gives the usual suggestions that my firewall/anti-virus/VPN, faulty cables/TM not having full disk access etc. must be the problem.

SOLVED! After weeks of experiencing backup failures, super-slow backups, and, yes, intermittent success with no clue as to why, I've figured it out: it's the screen timeout with screen lock/require password. I had tried everything discussed in the forums (turning off firewall, antivirus software, screensaver, etc.). But it wasn't until I turned off the screen timeout/screen lock/require password that it succeeded every time. Final configuration: I have Time Machine on manual and I turn off the screen lock once every two days and do the backup. Then I turn screen lock back on. Not quite as convenient as auto backups, but Apple is busy with OS26 and is not going to address this bug for us. I hope this helps all of you.

I was seeing 'Back up Fail' and then I realised that after upgrading to Sequoia Time Machine had decided to remember an old TM disk which it couldn't find because I'd got rid of it - literally thrown it in the bin. The previous system software sensibly just worked with the disk that was actually connected and didn't try and find the old broken one. But Sequoia decided to make it complicated. So it turns out that backups were working fine but the message I was getting was that they'd failed. Once I deleted the old disk from TM settings it was fine.

I have an M1 MacBook Pro running Sequoia 15.1.1 and it too could not complete the TM backup despite multiple attempts. I took the advice of an earlier reply and turned off the firewall before attempting another backup. With the firewall off TM backup went through with no problems. I don't have a need for auto backups and only do manual backups as needed so turning off the firewall, until Apple solves the problem, is not an issue for me.

Removing the Find My widget fixed the problem for me. Backups worked fine, then I added back the Find My widget and now I’m getting the error again after my iMac goes to sleep. We need a fix from Apple.

My backups of my MBAir with M2 fails under Sequoia 15.3.1. I cannot backup my laptop to any external drive. These backups have been working for years, so I assume failure is due to the recent installation of 15.3.1.

What to do?

Failure mode is exactly as described above "some individual system files that cannot be backed up". These files include MS Word "doc" files. Unlocking, removing or zipping the file simply results in another file failure to be backed up.

MBAir passed Disk First Aid. I find that Disk First Aid also fails on APFS with containers, so can't verify two different backup drives.

Problem might be the combination of Sequoia 15.3.1 and APFS, so I will reformat to HFS, and try again.

• I had no success backing up to my Western Digital (MyCloudEX2Ultra) since upgrading to Sequoia. Updated to 15.0.1 with same problems.
• I found an old post that suggested running this command in Terminal: sudo rm -f /etc/nsmb.conf (note: you may need to provide the password used to sign into Sequoia before Terminal will run the command)
• Since doing so, Time Machine has passed the prior errors and appears to be completing a backup on my MyCloudEX2Ultra via wireless network. As of this post, it reports 5 hours remaining (took <45 minutes to back up to a standard USB drive)
• Hope this helps