Time Machine Backups Exceed Allocated Space Following USB Drive Addition

[coolajami]

check the link below, they may give you a hint of what you want to try to see if something makes a difference.

Temporary solution to TimeMachine Backup issues (fails after the first backup)

So, you have and EX2 Ultra and, after recent updates, your TimeMachine backups stopped and now your Mac says something like “original disk can not be found” or backups once, then fails with “the backup disk is not available”. After a lot of ping-ponging with WD support I believe that I found the reason and (a working) solution to this problem. First of all, let’s check that you have the same problem as I do. Go to Settings → General → Time Machine → Configure and set the limit all the way righ…

Generally, I found the hard way that Timemachine is a great backup solution if you’re using attached drives as a destination, but for network drives, it’s pretty unreliable.