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

I do not believe this is specifically related to Time Capsule or WiFi. I have been using Time Machine to backup to a NAS for a few years without issue. Since the last several months I get this error on one of my machines almost weekly. The machine that fails is my Mac Mini with a direct ethernet connection to my network. My machine that has yet to fail is an iMac over WiFi. Go figure.

Just to add another voice to the discussion.

Late 2013 iMac running Sierra and same error message backing up to two different Time Capsules over ethernet.

Both Time Capsules are running newest firmware, one is an Extreme the other is older. No problems previous to updating to Sierra. Creating a new backup is never a problem but then error message occurs about 2 days later.

I actually noticed the problem consistently when I upgraded my Time Capsule firmware, not before, and I was on Sierra at that time. Either bad firmware for Time Capsule or compatibility issues with Sierra is my guess. Either way, its been happening for months with no response from Apple.

I've been using Google Drive for some time now and perhaps this could be a cause for issues? Just a guess. This may include other backup services such as Drop Box. I added the "/Google Drive" path to be ignored when running backups. I have these files synced to a separate laptop already. I moved the majority of my files to this drive folder just in case. Now, when Time Machine runs it doesn't find many changes and so the backup cycles are much shorter.

We'll see how it goes.

When I logged in this morning the error window was present again - about 3 weeks after the last full backup. Most recent backup is 3:29 am. I guess this is not going to get better. I plan to run a full backup again until I am able to try another option.

The only safe route is to follow TM instructions.

But to protect yourself to take a backup of the TM backup to another external drive at irregular times. I attach a disk via cable, do a simple drag and drop overnight.

I continue to have the issue with 10.12.4. I'm a Certified Apple Consultant and still have not found a remedy for this (for myself or for clients). I can't go more than 5 or 6 weeks tops without the error popping up, and no matter what I try, in the end, I have to start with fresh backups and lose the backup history.

Like others here, I'm beginning to believe this is a TC firmware issue. I'm also wagering that it's no coincidence that Apple stopped making and selling Airports and Time Capsules around the time Sierra was released, and this issue started.

I may try to see if I can downgrade the TC firmware from 7.7.8 to a previous version just to see how it goes. I'd like to get some more use out of this device since it's less than two years old. Without reliable backups, the TC is nothing more than an overpriced wireless router.

The collective wisdom seems to be that this problem is not limited to Time Capsule, as it seems to also afflict other networked Time Machine drives. The best solution I have found is to use Time Machine Scheduler (third party shareware) to set the backup interval to once a day.

Experiencing this issue as well, on both my iMac and MacBook Pro, both running macOS Sierra and both backing up to a networked 3TB Time Capsule. Seems at least once a week, either the MacBook or iMac will report "Time Machine must create a new backup for you". This is a bit of a pain. Everything seemed to work flawlessly since I've had the Time Capsule...well over a year.

I'll try Mitch's suggestion of running Diagnostics on the TC drive and see what it reports back.

That message is consistent with a Time Capsule hard disk drive that has failed.

If i select 'Start new back up', it takes about 24 hours to make first back up, backs up once or twice more then i get the error again.

That experience supports that conclusion.

Replace the Time Capsule. If you are sufficiently inclined, you can disassemble it and replace its hard disk drive, with some difficulty. Considering the rest of its hardware is probably OK, it's probably worth the effort.

I don't believe it can be a hardware fault as i alternate back ups between Time Capsule and a Synology NAS

and get the same problem with both. (This worked fine for at least 18 months prior to Sierra)

I really doubt the TC hard disk is faulty.. if it was.. the SMART error checking would give a hard disk error.. and the Synology NAS disk went bad at exactly the same time.. which should also give you an error. That is too much of a co-incidence.

I would strongly recommend you use a different backup software.

Try Carbon Copy Cloner or Chronosync..

The advantage of these software backup apps is they allow you to more easily select exactly what you need to backup.. so at least do a backup of your 1.5TB of photos and videos.. For and do a second copy to a USB drive. The personal nature of photos and the difficultly of recovery.. makes it imperative you make multiple copies.. infact I would get another USB drive.. self powered 2TB 2.5" drives are great and cheap.. and keep it with a relative.

As for your computer.. I would use CCC to do a bootable clone.. and then clean install the new OS .. or what you were using before.. then migrate from the clone all the files you want back to the computer.

I have this same problem as well - only started since "upgrading" to Sierra - a real PITA....

come on Apple - sort it out!

I grabbed a cheap copy of Acronis True Image 2017 from Amazon - it was $35.00, much cheaper than from Acronis' site.

Another corruption, that's 7 now.