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.