Backup fails bit it thinks it's succesful

I'm having problems with my file backups.

My files folder is over 30gb and a backup of it without styles is around 2gb when backing it up to private file. But when I backup to S3 it seems to only create a file around 223mb. When I download the file from s3 it's corrupt.

There's nothing in the Drupal log file to say it failed etc.

I get the same issue when running a quick backup in drush whether local or on my hosting environment.

My S3 bucket may potentially be not setup correctly as previously I was getting issues around object lock but I updated the permissions on my bucket. The error disappeared and the file size increased from 30mb to 240mb but it's still corrupt.

Any help would be appreciated, I suspect my bucket is not correctly setup.

Thanks Dan