What causes Time Machine to stall during backups?

I've had the same issue ever since migrating to a new M4 Mac mini, but never had the issue on my older M1 mini running the same OS version. Backs up fine when using the Mac, but not when it is locked. I've tried all the relevant fixes here (Firewall, that Find My folder exclusion, Spotlight reindex) to no avail. I back up to a NAS, and maybe related to this issue found myself needing to erase and reset my backups, but did that all within Time Machine, not by manually deleting the disk image.

Can't necessarily say this is more than an annoyance, as realistically the backups do work the only times files only on my Mac that I care about are likely to change (while using the Mac) and I back up just daily, but it is definitely annoying. Maybe we should wait for the next OS update and see if that changes anything, given the issues all backup tools are having in 15.2?

hi again, mr. luigi. i don't know if this will help anyone else, but i use an app called TimeMachineEditor (free at https://tclementdev.com/timemachineeditor/) to schedule my once daily backup at 4:00 (a.m.). again, i don't know if it'll help anyone else, but since i have a working (at the moment) system, i'll share whatever i have.

Hi dbreewood! Too bad 10.3 didn’t work for you. I thought I’d help you out with a little feedback about your widgets hypothesis. If others do the same, maybe you can track down an offending culprit. My wife’s M4 Mac mini had the TM problem (until I switched to Carbon Copy Cloner 7). The widgets she was using when TM was ravaging her were Weather, Calendar, Battery, and Find My. Hope that helps. This is a good mystery. Better than most.

Hi dbre! Before posting, I have developed the habit of copy and pasting any comment I write here and place it in a folder in the Notes app in case I need to retrieve it. Ironic that I backup comments in a discussion about TM backups! Am I correct in understanding that 15.3 did NOT solve the problem but then you tried removing certain widgets and that DID solve the issue, hopefully permanently? As a retired teaching scientist, I can't help but be curious what would happen if you added back the suspicious widgets to confirm your hypothesis. (One of them could have been corrupted. A one off sort of situation.) But, if TM problems return, that sure makes those widgets look guiltIER. But BEFORE removing them, I'd update to 15.3.1 and see if that solved the problem. If 15.3.1 solved the problem WITH the suspicious widgets still installed that would seem to be a better situation for you as you could then avail yourself of those widgets with impunity. I apologize in advance for suggesting you do even more work on top all the investigative effort you have already done. I'm just a slave to my curiosity.

The error returned yesterday after 37 Days, 5 hours, 3 minutes of no issues.

I then carried out:

• Quit out of Apple Books which I'd started using again earlier in the day, and had imported some ePub books
• Reformatted an external derive I use for Carbon Copy Cloner backups on some files from my NAS, as CCC reported the drive was full.
• The 'Use iPhone Widgets' on the Mac was turned off again. After the latest MacOS update it had turned the option back on.
• Emptied the rubbish bin
• Rebooted the Mac

Everything seems to be backing up normally once more.

You do not need to wipe out the NAS partition. It works if you just delete the appropriate sparse bundle.

Also, make sure that you don’t turn on the Firewall again.

Later on I had a TM backup failure again, but rebooted the Mac and it seems to have resolved it. Maybe some data from the Home widget was kept in memory?

Still an issue in 15.4 on M4 mini. I've now excluded the FindMyWidget snapshot file and disabled widgets entirely. Will see if the "unavailable file" message recurs.

Yes so I ended up wiping the Mac and doing a restore from a backup. I got a conflict when restoring which I ignored.

So yep it didn’t restore properly so I’m doing it again this morning. Interesting when it downloads the OS to do the reinstall it uses Sonoma.

So while the OS part of the restore is taking place it’s our early doors for a coffee.

I will be going back to using Sequoia even if it has the problem again so I can feed back to Apple. I know from past experiences cases are help open for 30 days.

In any case, at best it might be addressed in 15.2 or 15.2.x with any luck since as you found out, the support team is not aware at large of the issue as you found out. According to the second tech support person I chatted with yesterday said that the “engineers were aware of it”. However, with 15.1 the issue is worse than with 15.0.1.

I do not see it listed in known issue or an official explanation by Apple in the support pages. There is another thread specific to NAS backups failing: What causes TimeMachine backups to fail o… - Apple Community .

Not good.

The reinitialisation of Spotlight indexing, after 2 attempts is working this morning. I'm keeping my fingers crossed that this will continue work. But I have had intermittent Time Machine performance before, using other methods of remedy. Thank you for your suggestion.

I spent time with Apple Support — supposedly a Mac Senior Advisor — who basically had no real answers to my questions:

[1] He did not commit to say that turning the Firewall would continue to be a workaround for 15.1.1 as it works for me in a MBP 2021 M1 Pro and 15.0.1.

[2] They are still investigating the issue with 15.1.1 and do not know if and when the issue will be resolved. I pressed onto the Senior Advisor that issues with Firewalls and Time Machine were not minor and Apple should not sweep them under the rug. Again, no commitments from the SA.

[3] I filed a complaint that one of the Advisors (first level support) insisted that I upgrade to 15.1.1 and then contact them again if that did not fix the issue. My bone was that I would not do it if it meant that “my” workaround (turning off the Apple Firewall) would not work. They could not answer that.

Has anyone here using 15.1.1 tried turning off the OS Firewall and testing if the backups complete without issue? Or they are are also failed?

I format the drives manually as 'APFS Volume • APFS (Case-sensitive, Encrypted)'.

Interesting in removing the drive and re-adding after a reboot. I've done this before and T M has never reformatted the drive, just used what was already there. Next time it fails I'll try adding that schema into my 'fix' notes :)

I've given up on Time Machine. Far too many problems over the years. I've lost all my history three times so far. After upgrading from macOS 14.7 to 15.2 Time Machine started failing. It would stall/fail during the night trying to complete a backup. No idea why, no idea how to fix it.

Then Time Machine deleted over two years of history! Now that everything is lost (again), I reformatted and tried with a clean drive. Again, failed during the nightly backup. This happened two years ago, and then I lost about three years of history.

Sure, clicking "backup now" would complete a backup but here's the question: How do you know it really worked? Have you tried to to restore? Even when it completed the backup I find many errors in the logs. I find the same errors many other have reported with macOS 15.

So...I do not trust Time Machine, and after so many years of losing backup history I'm done forever.

Now I'm using Carbon Copy Cloner to create backups. Works really well, twice as fast, and does everything Time Machine ever promised and much more.

Hi bruiselle! I wanted to report back on my experience directly plugging my two backup HDD into the M4 Mac Mini. Since I already have used two of the Thunderbolt 4 ports in the back of the Mini, I could only plug one of the backup drives into the back of the Mini. I plugged the other backup HDD to one of the 3.1 USB ports in the front of the Mini. I woke up this morning to failure again. I am going to try one more thing. I removed the backup HDD that was connected to the front of the Mini and also removed it from the list of backup drives for TM. So now I have only one backup TM drive and it's connected to the back of the Mini via a Thunderbolt 4 port. Let's see if this works. I prefer two backup drives, but if this works, I'll go with it as I also use Dropbox and Sync for all my documents, etc. BTW, when you said you solved the problem by directly plugging your backup drive(s) into the Mini did you mean using the Thunderbolt ports in the back?