What causes Time Machine to stall during backups?

I've had no trouble with Time Machine until updating my Mac Mini M2 to OS 15.0.1. After the update, I constantly get the message "Time Machine did not finish backing up because some files were unavailable. Backups will resume when your Mac is unlocked." The backups seem to run fine until reaching about 80% then stall before the message appears. I've tried different ports, different USB C hubs, different cables etc. with the same result. I've scann the resources here and found nothing current or helpful on this issue.

[Re-Titled by Moderator]

Mac mini (M2, 2023)

Posted on Oct 25, 2024 05:25 AM

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Kerry Kinkade Author

Level 1

45 points

Posted on Oct 25, 2024 02:50 PM

After my initial post, I tried erasing my backup drive and starting over with a new time machine backup, but I still got the same message.

After exhausting everything I could think of, I called Apple Care. I spoke with a representative who let me explain everything I had already tried and he indicated that I had covered most of his solutions matrix, so we didn't waste time going over that again (GREATLY APPRECIATED!). I was put on hold for a short time by the rep then asked to do the following:

Eject my backup drive and disconnect it from my Mac;
Open time machine and tell it to forget my backup drive;
Restart my Mac in Safe mode;
Reconnect my backup drive;
Open time machine and tell it to use my backup drive for a new backup;
Let time machine format the backup drive and complete an initial backup to my backup drive;
Confirm the initial backup finished without errors;
Restart my Mac in normal (not safe) mode.

I completed the above steps in pretty short order and have since had 5 hourly backups with no errors. This seems to have solved the problem.

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141 replies

Dec 29, 2024 07:56 PM in response to Kerry Kinkade

Please, provide Apple with documentation of your experience via Apple Feedback. Here is the link to Apple Feedback for the Mac Mini. Feedback - Mac mini - Apple

envoy510

Level 1

47 points

Nov 15, 2024 05:47 PM in response to Kerry Kinkade

It's just lazy customer support to ask users to wipe their TM drive and/or Mac hard drives (and restore or reinstall macOS). There is obviously a NEW bug in macOS 15 that is causing this when TM kicks off and the screen is locked. Obviously. Wiping everything only papers over the problem and DOES NOTHING to find the real issue.

I say "lazy" without any guilt. I do customer support for a software company and I always want to find the real cause rather than paper over it. Look how many people are impacted by this!!! The real number is 1 or 2 orders of magnitude more! (because people don't spend the time finding a place to post their problem)

dbrewood

Level 2

168 points

Oct 29, 2024 03:56 AM in response to mjmarch

Okay thanks I'll format the external drives and wipe the NAS partition then before going through with the procedure.

mjmarch

Level 1

121 points

Nov 1, 2024 08:19 AM in response to dbrewood

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.

mjmarch

Level 1

121 points

Nov 1, 2024 08:19 AM in response to dbrewood

Does anyone know if Apple fixed this problem in the upcoming Sequoia 15.1 update?

dbrewood

Level 2

168 points

Nov 1, 2024 08:25 AM in response to mjmarch

Eh..... turn off the Firewall? Why? Are there issues with it?

I would have thought it'd be a major security issue if it was turned off?

dbrewood

Level 2

168 points

Nov 1, 2024 11:21 AM in response to mjmarch

Indeed I do!

Heck I'd not heard of it causing issues (or causing this one), is it a known issue?

dbrewood

Level 2

168 points

Nov 1, 2024 11:22 AM in response to mjmarch

Understood, hoping they do fix it in 15.2!

dbrewood

Level 2

168 points

Nov 3, 2024 01:25 AM in response to mjmarch

I quite agree. I did point them at this thread. They need to take the issue on board and resolve it.

dbrewood

Level 2

168 points

Nov 3, 2024 04:51 AM in response to Kerry Kinkade

I'm now fully restored and back to running Sequoia 15.1, so let's see if the issue reoccurs ....

Misterar

Level 1

59 points

Nov 5, 2024 01:06 PM in response to Kerry Kinkade

Me too.

I'm just using an external drive and never(!) had any issues with it before 15.2.

I've tried everything to fix it. Nothing works.

mjmarch

Level 1

121 points

Nov 16, 2024 06:22 AM in response to dbrewood

I am waiting for 15.2. I do not dare to break out from the workin 15.0.1 I have.

envoy510

Level 1

47 points

Nov 16, 2024 02:22 PM in response to dbrewood

I've disabled spotlight on all local drives, so I doubt it would help me.

Nov 19, 2024 03:47 AM in response to Kerry Kinkade

這真的很酷現在真正知道了

Nov 21, 2024 04:09 AM in response to Kerry Kinkade

So has anyone else tried installing the OS 15.1.1 update? I did, and TM is working for two days now.

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What causes Time Machine to stall during backups?