Nextcloud backup to S3 reads from S3 a lot

Nextcloud version: 23.0.4
Operating system and version: ubuntu 20.04

I’ve been using backups to external s3 storage for a month and realized that they eat all my money. The problem is that nextcloud reads data every night, even if no backup is created. Storage itself is not that expensive as read requests, and it feels like I don’t need them:)

What generates this load? How can I turn it off?

Is this with the backup app (then we move to the correct sub-forum)?

Yes, with the backup app.