Time Machine reporting thousands of errors: setattrlist failed for path '/.MobileBackups/Computer/
It may relate to this and/or help someone else figure out more about this but when I look at directories that are subject to the failure on my Mac, I see:

    sudo ls -al@ '/.MobileBackups/Computer/2016-11-05-233040/Volume/Library/'
    total 0
    d------r-x@ 4 root  wheel  136 Nov  5 23:33 .
        com.apple.backupdelta.MoveChecked     3 
        com.apple.s stem.Security    68
    drwxr-xr-x@ 5 root  wheel  170 Nov  5 23:30 ..
        com.apple.backupd.SnapshotVolumeFSEventStoreUUID     36 
        com.apple.backupd.SnapshotVolumeLastFSEventID    20 
        com.apple.backupd.SnapshotVolumeUUID     36 
    d------r-x  5 root  wheel  170 Nov  5 23:32 Application Support
    d------r-x@ 4 root  wheel  136 Nov  5 23:33 Preferences
        com.apple.backupdelta.MoveChecked     3


I imagine most of these file attributes are related to Time Machine's local backup process, but I also notice that one of the attributes is com.apple.s stem.Security .. note the blank character in the system path component.  Could that be confusing things?  For example, if that attribute was set with that typo and later cleared (or attempted to be) with it spelled correctly, you would see an error like this.

Just guessing ..