What causes TimeMachine backups to fail on NAS devices?

I can't even restore to prior time on my Time Machine to prior update. But it says it can't do it because it says the library files can't be modified or deleted because they are needed by mac. It's useless. 2023 expensive MacBook Pro that is now absolutely useless...can't even use both monitors unless I plug them in manually AFTER I turn my computer on.

I back up to a Synology NAS using Time Machine and it worked yesterday and not today after 15.0.1 update

"The network disk disconnected from your Mac while backing up."

Mine gets to 0MB. But with a film playing off the same NAS during backup gets to 95 MB then goes to 'skipping'

I've been using Time Machine to a QNAP NAS for years and once I upgraded to 15.0.1, it stopped working. I even wiped the backups from the NAS and set it up from scratch, but it won't even start the first backup. Disabling the Mac firewall does not resolve the problem.

I bought a new M3 MBA, installed 15.0.1 and migrated an old Intel MBA to it. T-M backups failed. Rather than go the long haul route, I shall downgrade the M3 to Sonoma 14.7.1 and reinstall.

Meantime, I've reported this direct to Apple executive relations.

Im having a similar issue. We use a Synology Nas to edit footage from. Its been fine for near on 2 years. I updated (mistake) 2 weeks ago and then all of a sudden monday monring the server is disconnecting whenever it needs to do something ie: Exporting a video, reading the timeline, importing photos. It doesnt seem to matter about the file size. It just disconnects. Any ideas here? its only an issue with the NAS. Other drives like the Black Magic Cloud unit is fine. Also transfer speeds have slow right down

For the past year I've been running into bug after bug after on MacOS. Now this again. It's getting rather pathetic. Apple needs to up their game and start delivering what they promise and preach. This TimeMachine/firewall thing is again another day of Apple issues. I can hardly consider this 'Pro'. This stuff breaks flow.

You know what would be ballsy. If Apple would refrain from a MacOS release next year and just fix all of the bugs and refactor the OS to an extend that their primary workstation OS doesn't feel like somebody's hobbyproject abd an experiment in quality control abstinence.

I did this already with 15.0 + 15.0.1 and that fixes it also temporary, but I came back after a while. Will try this as well with 15.1 but this shouldn't be the solution to remove the whole backup and start again.

That because it Disney at every Mac Upgrade each year! That’s why I consider Time Machine to to basic and myself went shareware backups that continue programs instead where it picks up older backup files!

You're out ahead of your skis. Worse, you're smug about it. It's clear it is not caused by third-party firewalls, or even Apple's firewall - I don't have a separate firewall, and Apple's is turned off, and I still have the problem.

To be clear, it's not clear what is causing the problem.

It does seem likely that you're repeating yourself.

I have the same NAS setup. My Time Machine backups (scheduled and manually invoked) have failed with the installation of the Sequoia 15.1.1 update, for a variety of reasons - eg: network connection dropped. They might progress a few MB, then fail. Was working perfectly before then, and there's not been any other changes to my NAS or network.

I have tried all of the above suggestions, and much more, but no go.

Whatever the security issue the update "fixed" was clearly some serious sh1t that it's broken other things in the process. I just wish they'd explain what it was they did - but I guess that'd help the bad guys...Meanwhile, hoping Mac's hard drive doesn't die anytime soon!

Not to beat a different dead horse but there is another major problem introduced with OS 15: typing lag with long entries in Messages and in Notes. Also OS 15 has not fixed the perennial problem with Messages not updating. This second problem has been around since OS 14. My workaround is turning off and then turning back on wifi which is what I did each morning and now still have to do with OS 15 and now under OS 15 I have to do it several times a day. I am convinced they are 100% aware of these problems but either have no solution or more likely just not motivated in fixing them.

So there have been quite a few posts on this thread now regarding failure of Time Machine to backup to a NAS.

In all fairness before totally apportioning blame to Apple, can posters please indicate what NAS they are using, to determine whether or not it's just one brand of NAS that is affected eg,Synology (in which case equal blame can thus be apportioned and followed up), or across a number of brands.

It's just not clear if there's a common element here besides the Apple security update -and being more specific could help provide a solution. Thanks!

Nope. Other reports in the boards indicate that 15.1.1 does not fix the issue. Depends on some obscure configurations. I have tried to get reassurances from Apple Support about 15.1.1 not breaking my workaround but they do not give even that reassurance while pushing updating to 15.1.1.

Even people who did a clean full install of the MacOS had issue after they painfully restored everything they had.