Amazon S3 very slow internet

I run SyncBack every day with no performance issues.

I just started using Amazon S3 for the first time for a small backup. This morning I did an update backup and my internet access slowed badly. My normal download speed is over 6000 and while SyncBack was running it dropped to 1000 to 1500. As son as SyncBack completed the speed went back up.

Also the update backup tool 30 minutes - and that seems very high, for the number of files and files sizes, especially when there were few file changes from last night. Fastbackup - overwrite to S3 - versioning on S3 -

Is this normal?