iMac and Mojave Time Machine issues

[PWC1141]

After updating to MacOSMojave I could not back up via Time Machine on my iMac even after erasing and checking my external drives. Finally I saw an option of choosing "case sensitive" when reformatting an external drive and after that a full back up was possible. Not sure why this occurs but maybe this can help anyone with similar issues.

 

[carbontune]

I did not have this issue at all. My 2017 iMac arrived with High Sierra and a few days later I upgraded to Mojave. I'm still using my old Time Machine external drive via a USB 3.0 port. What options did you choose to format your Time Machine drive?

 

[PWC1141]

Originally I had the external drive formatted as non case sensitive and nothing worked until I changed it to case sensitive.