Time Machine completed a verification of your backups on “Time Capsule”. To improve reliability, Time Machine must create a new backup for you.

I am approximately 100% certain that the culprit here is Sierra. We have two iMacs of the same vintage (a year old). One is running Yosemite and the other was updated to Sierra. The former still backs up to our Time Capsule every hour without issues. The latter fails verification every week or so. I ran Disk First Aid on the Time Machine disc and it reported:

The volume Time Machine Backups was found corrupt and needs to be repaired.

File system check exit code is 8.

File system verify or repair failed.

Operation failed…

Yet this Time Capsule has no problems backing up the Yosemite iMac, only the iMac running Sierra.

I definitely have the same problem since I upgraded to OS Sierra!!! Before this I had backups from the past 8 years from my previous iMac and all previous versions of OS X. At the moment I lost them all... hopefully the hard disk of my iMac is working properly... yet!!! Otherwise I would have nothing...

I too have my iMac connected to time capsule by gigabit ethernet cable.

Let me illustrate you what I get (it's in portuguese of course) but you can understand from the format of the error message that it's the same problem.

Since the first time I got the error message (only after my upgrade to Sierra): I naively accepted that as a warning and performed a new backup... only after its completion I understood that I had lost 8 years of well done backups! I said it's ok, since I had a brand new iMac, and I had just installed on it all the data by restoring it from my previous backups, trusting that the error message won't happen again. First new backup run well, and I was happy at that, but 2 or 3 days later I got the same error message. I tried to follow all the advices from Apple support, regrettably none has been issued for OS Sierra, the latter available regarding Yosemite, and none has helped. Re-installed OS Sierra, assuming that it could have been some corruption on file system, and no success again, the error went on and on...

Tired of this, I decided to erase all Time Capsule disk, using Airport Utility. Performed a new backup, which was successful as you can see (the window shot was taken today, the 01/18th):

so, we had it running well for 8 days until today, when the same error message pops-up again!

So, from all the above, it's definitely NOT an hardware problem of the Time Capsule, since I'm not seeing a problem that only reveals every 8 days or 2 or 3 days, whatsoever. It's definitely a Sierra problem managing the old Time Capsule devices, firmware 7.6.8 (it the last available update for this type of Time Capsule).

I am appalled by the fact that I'm reading several iMac users complaining about the same error, for some months now, and Apple seems not to be concerned by this that much!

From my part, I've given up trying to perform new backups all the time, as I'm pretty sure that sooner or later I'll have to resume the procedure from scratch ... no way, this is not a solution! This is not a Time Machine, this is a "Time Wasting Machine".

Last but not the least, the on-call support that I could get from Apple was useless, although the politeness and promptness of its service engineers. Regarding this problem, it becomes a very time consuming discussion, and all the attempts to solve it that can be performed take too long since we are dealing with Tbytes. It's not worth it!

So, can anyone help on this? Time Capsule is too expensive to buy a new one and fall in the same situation...

Much obliged for your attention.

There are numerous people having this problem. My TC is less year old, was working great until macOS Sierra and my new MacBook Pro 15". This thread:" Time Machine constantly making new backup " appears to have a constructive conversation about the issue.

I see your point, distinguishing a network drive (even hardwired via ethernet) from a local drive. In this thread, which I notice you are also following, someone appears to be saying that they had the same problem with a Firewire drive. I could be reading it wrong or it might be an anomaly. I am getting to the towel-throwiing stage of buying an external USB drive dedicated to local backups, nuisance though this would be.

Time Machine constantly making new backup

YatBob wrote:

Saw this posted in a forum, nt sure what it means but may have some bearing on our problems

Apple added support for SMB sharing to Time Machine in Sierra. The SMB developers are currently making the changes. One commenter mentioned that you could get better results when you are sharing an actual HFS+ file system instead of a sparse image.

Apple changed over to SMB as the default network protocol at Mavericks.. if memory serves.

And we have seen since Sierra that mounting the Network Drive (TC) manually as SMB was important to get functionality of say clicking a file and it opening the required application.

If Time Machine which is much more highly dependent on AFP protocol and up to Sierra still used AFP for backups even when it was SMB for everything else.. that would indicate why Time Machine is having so much problem. AFP and HFS+ were kind of hand in glove with each other. I doubt breaking that connection will be easy. That is assuming the comment is correct from YatBob but it does sound sort of like what could be happening.

I would be interested in what happens with Carbon Copy Cloner or one of the other well known third party backups to Time Capsule.

I also wonder if turning down the SMB security could help.

See Turn off packet signing for SMB 2 and SMB 3 connections - Apple Support

I turned off packet signing due to the speed issue.. I was getting really poor transfer speed and turning off signing helped enormously.. but I wonder if corrupting backups would be a side effect.

I have moved more heavily now to CCC.. although TM is still running.. but I like CCC more and more. It gives simple reports on each scheduled backup of what it has done and if it failed it simply tries again later.

Would love to get some more input from others on this as I'm having the issue at Mitch. iMac running Sierra keeps throwing back errors while MBP running Yosemite is backing up fine. I tried to use a LaCie external hard drive as my time machine backup for 2 weeks on the iMac and had no problems / errors.

i have a similar issue except i have one Mac that gets the error and the other backs up fine. both are running sierra -one is a 2009 iMac the other is a 2016 Macbook Pro. Macbook Pro backs up as it's supposed to, iMac keeps getting error.

Same issue here w/Sierra. I've had to recreate my backups now 5 times. I've since also replaced the TC disk, and the problem still occurs.

Backups prior to Sierra were fine for years, now w/Sierra I cannot retain a backup for longer than a few weeks.

I have the same problem now. My problem started immediately after updating the firmware on the Time Machine. I've been running Sierra since it came out (always with the current edition) with no issues on either my 1TB Time Machine or my 3TB Time Machine. No longer using the 1TB for backups but the 3TB starting screwing up the day I installed the firmware update.

That's a good point about the firmware. I'd forgotten it was updated about the same time for me as my Sierra update. It could certainly be that is the cause. Either way, its a deal breaker in terms of using Time Machine. I've had to invest in an alternate backup program to ensure my data is backed-up and safe.

the time capsule firmware is a possibility... my backups are being corrupted every couple of weeks and it can't continue.. can I ask what alternative backup software you have chosen in lieu of time machine? as I'm going to need to explore alternatives

Two weeks having elapsed since my last forced new backup, I decided to run Disk First Aid on my Time Machine disk, knowing if I waited for it to fail, DFA can't repair it. DFA found a massive list of errors (far too lengthy to post the transcript here). In the end DFA reported making a huge number of repairs, and then at the very end of the process, reported that a repair had failed. However, the next backup was successful, so I don't feel any worse off.

My plan is to run DFA weekly in hopes that it will prevent a future failure, or at least stretch out the time between being forced to start from scratch. If anyone else with this problem would like to attempt the same fix, here are the steps:

Launch Disk Utility.

Force Time Machine to "Back Up Now"

Wait for the Disk Image "Apple sparse bundle" to appear in the list.

Select the volume "Time Machine" under the "Apple sparse bundle" toggle (quickly, as it will only appear for as long as the backup requires).

Click the First Aid button.

Wait (took about an hour for me)

The issue is backup over network.. for iMac plug a USB drive into the computer.. and do local backups for the time being.. most people seem to have no issues with local .. only network. At least until Apple fix this one.

The other recommendation I have made is to use Carbon Copy Cloner or a similar backup third party app. You will find it backs up to the TC using a sparsebundle the same as Time Machine.. but I am unsure if it will fix the issue. which I am pretty sure is network problem.

I am using a late iMac 2015 with an old Time Capsule 3rd Gen 2010. I am likewise having this same problem for months and assumed it was more likely the old TC. Last month I spoke with Wireless Senior Apple Support and they had me upload to their engineering dept my TM logs. I was told they would get back to me which never occurred. I just called back and was informed that since I submitted my log, engineering has determined that this is a known problem with Sierra 10.12. There is no known fix currently and hopefully the next update 10.12.3 will fix the problem. In the meantime, they rec connecting a separate external hard drive via USB or thunderbolt as the problem only occurs with TC which is a network drive. A 3rd party drive will work fine and TM will alternate backups between the two drives. Once the problem is fixed, TM will no longer keep prompting for a new backup. Another option is to temporarily disable TC and turn it back on after future 10.12 updates.

I ran DFA again on my Time Machine disk, and this time it reported no errors. I am now on my third week of not needing to create a new backup. This is the longest interval since I installed Sierra so I am thinking this workaround might be worth trying.