Since upgrading my MacBook Air to High Sierra I cannot get Time Machine to backup onto my Time Capsule. Everything has worked perfectly until this update however now, it takes hours and then fails with a simple 'cannot complete'... frustrated to say the least.. tried everything i can think of even deleting preferences and starting MBA in safe mode... help please...
MacBook Air, macOS High Sierra (10.13.1)
I hope you've solved this already.
I had a similar problem, but in my case High Sierra Time Machine backups worked for a time, then went crazy last week and died.
Erasing the Time Capsule and restarting it clean resulted in a never ending first backup. Last night (2018-01-12) I found a suggestion to omit the folder "~/Library/Mobile Documents" from the backup in Options button in Preferences --> Time Machine.
My backup complete properly overnight with this.
I was looking for that thread to mod up the answer when I saw this one.
High Sierra - Time Machine - Time Capsule
