Time Capsule Not Completing Initial Backup

Hello, I just recently purchased the 2013 3TB Time Capsule. I started backing up wirelessly.. which I knew would take weeks/months so I disconnected it and hooked it up to my mac mini directly via ethernet cable while using my old time capsule for regular internet access. When this was all apparently done, I moved the new TC back into position as my main internet source (removed the old TC out of the network altogether).

I then checked the backup button by presing "back up now" and at that point my system reported that it was backing up 39 GB (which later grew into 79 GB). I let this complete over the air... A day and a half passes, the backup seems to complete because the backup process seemed to have stopped. However the latest backup is still days ago ("June 24th). Somehow the 39 GB is not being backed up so the process is starting all over again.

Can anyone tell me what is going wrong? I would hate to have to go through the entire days long initial back up process again. I have 800 GB in total to be backed up.

Note; This is an encrypted backup so not sure if that has anything to do with it.

Note 2: Part of what needs to be backed up is on an external HD (music/software backups).