Amazon S3 Pruning Error

I been having this error since my VPS was upgraded to Centos v7 cPanel v64. Backups ARE transferred to S3 without any apparent problem, but I get an emailed error message after: "Backup transport errors" // The system encountered errors during transport of the backup files. Below is a preview of the attached log file. Preview of transport errors log: Unable to prune transport "S3 Backup" Unable to remove outdated backup: The server has stopped responding at /usr/local/cpanel/3rdparty/perl/524/lib64/perl5/cpanel_lib/Amazon/S3/Bucket.pm line 333. This notice is the result of a request from "cpbackup". // At Backup Configuration, 'Validate' shows the error: Error: Validation for transport "Backup to S3" failed: Could not list files in destination: The server has stopped responding at /usr/local/cpanel/3rdparty/perl/524/lib64/perl5/cpanel_lib/Amazon/S3/Bucket.pm line 333. I deleted and re-entered the S3 account backup, but 'Validate' still shows the same message. (I assume the backup still does actually work as before, so the access keys were fine.) My backups are about 12Gb. I've been running this same backup for nearly 2 years and haven't seen this error before. It began immediately after the cPanel update (from v56). I wondering... is it trying to remove the "outdated backup" at S3, or on my server?? It won't have permission to remove the older S3 versions.