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 even more highly recommending the procedure I outlined above for running Disk Utility First Aid on your Time Machine backup on at least a weekly basis. This week it found numerous errors, which it repaired successfully. Time Machine has not required starting a new backup since I began this procedure a month ago. So this workaround seems well worth trying for everyone experiencing this problem, at least until Apple pushes out a real fix.

Well, just gave up on trying to fix it...

Just found one workaround which is, if you don't need automatic backups being performed simply deactivate this function on Time Machine Preferences and do it manually once a day. It works, and it's more than enough if u don't have your Mac changing that much on an hourly, even daily, basis!

Unless Apple puts an official fix for this bug, it will never be fixed and all the proposals here will be mere workarounds...

Wish you luck.

That's actually a great idea. Since it seems like practically every morning I get told my backup failed verification and I need to make a new one from scratch, which is over 100 GB of data, why not just do a quick manual backup first thing in the morning, which will only be a few MB!

FWIW, it's not just Time Capsule, it is, as someone else stated, backing up over the network. I'm using a Mac Mini with 2 external USB drives and OS X Server as my backup target for 2 Macbook Pro laptops running Sierra, and I am getting the "Time Machine has completed a verification..." errors every 1 - 10 days on either client on either backup target. Disk checks always come out clean, and every time I've done a manual verification of the backup (by holding down Alt) it's clean.

I'm hoping Apple fixes this in 10.12.4 as it's really impacting my enjoyment of the otherwise great OS.

This issue has been going on for a few months now. Time Machine is broken and Apple has decided to abandon it (just like the Time Capsule). There isn't anything you can do to fix this problem. Apple has no solution.

Only thing you can do is fine a different backup solution.

Only a theory but I am wondering if one faulty backup might not sometimes be enough to corrupt the disk image sufficiently that TM can't handle or correct it on the next try. Other times it might be the cumulative affect of multiple corruptions. Either way only Apple can figure out why this is happening and fix it. In the meantime I am going to continue to run prophylactic DFA diagnostics and repairs on my TM. It's held up for a month now, which is longer than before, by a lot.

You're way may still work!

Looks like human error on my part. On my last DFA pass I wasn't paying that much attention and I thought to myself, wow, that ran fast. But it appears the sparse bundle wasn't actually mounted. As, I noticed today when I tried to follow up on your suggestion on trying to run DFA after the failure.

no. You post this everywhere someone complains about this. The hundreds of threads about this error since Sierra dropped are not a coincidence. My backup fails EVERY MONTH on my Sierra MBP.

I'm using the same Airport Extreme and a Synology as TM and it has worked for years, and my MacMini with El Capitan is STILL backing up hourly to this disk with no problems. The only issues are after upgrading to Sierra.

Apple needs to address this, but I know they ignore these forums and will never admit anything.

once a backup has been flagged as 'failed or corrupt' it can never be used as a backup again. You can possibly open it in TM to browse it or copy files, but its done as a backup.

This is def a Sierra bug, that Apple needs to address.

Bad news on that front. My backup failed a couple of days ago, after about a month, and only a couple of days after running DFA on it. So this method might still lengthen the time between failures but it seems as if it isn't going to prevent it entirely, and even a few days are enough for the backup to become corrupted beyond repair. Maybe it can even happen with one backup.

More failures for me too (8 now). I'm getting to where I'm losing faith in Apple's ability to provide a reliable, stable system. That's not good for us. The Time Capsule is now nothing more than an expensive, moderate router.

Get your act together Apple, and recognize that backups are important to your users!

I find it absolutely absurd that a problem of this importance is taking Apple so long to address. What is the sense in doing backups if you can't depend on the backup mechanism, and a pricey Apple mechanism to add?

My most recent backup failed while I was running DFA on it! I don't know how this is even possible, but it happened.

My next workaround is going to be using Time Machine Scheduler. Perhaps backing up less often will help. I don't have a lot of confidence, but it seems to be worth a try.

http://www.klieme.com/TimeMachineScheduler.html

We don't know we can't.

It's not like the TM backup is corrupt, there is just some issue according to Apple's heuristics.

It may well be something that would cause a new backup to fail, but that doesn't mean the old one can't be read.

why remove the old

The old backups are corrupted, and of little to no use.

And 1TB each time anew copy takes a while

The new backups will occur at maximum speed if you connect an Ethernet cable from your Mac to one of the LAN <--> ports. Be sure to turn off the WiFi on the Mac before you start the backup.

If you have been using wireless to back up in the past, the Ethernet connection will usually go at least 2-3 times faster than wireless.

Sometimes the Time Machine backup can still be accessed after receiving this notification, other times not. I think it is approximately 100% certain that the backup is corrupted. Running DFA on the TM disk periodically reports corruption on the disk image, and sometimes can repair it. Other times it reports corruption, but cannot repair it. In every case so far where TM throws off the verification error, it is too late for DFA to correct the issue, whether the TM backup can be mounted or not.

It is totally mystifying why Apple has not addressed this problem. It is clearly related to Sierra. They just need to go back to the prior version of whatever they changed.