This is the 2nd time I got this error message:

enter image description here

On my Mac Pro, I use two HDs for Time Machine backup. Time Machine would use them alternatively. The other HD works fine. With this HD, I used Disk Utility to perform "First Aid" and no problem was found. However, the Time Machine still cannot back up to this HD.

On the previous error, I had to reformat the HD. Any suggestions on what I should do this time?

  • Are the disks formatted the same way on both?
    – Natsfan
    Commented Sep 25, 2018 at 20:41
  • The one that failed is formatted as Mac OS Extended. The other one is Mac OS Extended (Journalized). Commented Sep 25, 2018 at 21:30

2 Answers 2


It turned out that App Cleaner is the root cause of the problem. I used App Cleaner for quite some time and have purchased the premium version. My problem with App Cleaner started with its V6.0 version and I was still on High Sierra. So it was not a Mac OS problem.

  • did uninstalling the app correct the issue?
    – ScottyG
    Commented Apr 3, 2019 at 14:51

Here is solution:

https://discussions.apple.com/thread/8561149 I tried just now and works.

  • Welcome to Ask Different! While this link may answer the question, it is better to include the essential parts of the answer here and provide the link for reference. Link-only answers can become invalid if the linked page changes.
    – Tetsujin
    Commented Oct 21, 2018 at 15:44

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