I am getting this message when trying to backup data. I searched for this topic in this forum and found a similar entry posted several years ago and the issue was not resolved. This started, I believe, after the recent firmware update to my 3T time capsule. Airport Utility/disks displays this device has 1.36T free. the disk utility says it has 0 KB free. As I write this, I am running Disk Utility first aid but it seems to me it is not advancing, but I am letting it run at least for one hour more to see if it completes the task, which I doubt it will. If this process fails, what would be the next step I should take? Thanks for your help.