Time Machine backup constantly transferring 30gb+ I have mac book pro mid 2015 with high sierra.  I backup to time capsule network drive.  Initial backs ups transferred like this.

day 1 250gb
day 2 80gb
day 3 60gb

It would then do small backups regularly with no issues, which corelates with my daily usage but on day 15, it started transferring 30gb+ again.  So whenever I do have laptop open, it never completes transfer or backup. Latest complete backup is maybe a week ago.  

I use the laptop every day, but apart from a few music album downloads, I'm not a heavy downloader.

My total space used is currently 257gb (500gb total).  Only thing I can think might cause it to act up, is I have some VMs on my machine that might cause it to think it needs to transfer those images constantly.  I have google drive, and icloud for offline backups. 

Edit: How can I stop this from happening, and create a backup.
I  use the application BackupLoupe to examine my Time Machine Backups. This enables me to see what is in each backup and then set exclusions as appropriate to meet my needs.

The biggest exclusion is the folder my virtual machines are stored in. I never allow Time Machine to backup my VM's.

System Preferences > Time Machine > Options... > Exclude these items from backups:

Note: I have no affiliation with soma-zone the developer of BackupLoupe.