[Plugin: BackWPup] scheduled backup to s3 never completes (but manual works fine)

running the latest version of this plugin and have a scheduled backup to s3 to run daily from 6am (usually whenever first visitor hits blog after then)

however the scheduled backup triggers but never completes, viewing the log it stops at this step:

2010-07-19 07:22.43: Connected to S3 Bucket: <mybucketnameremoved>

the backup file never gets put on s3 and the process never completes (i have to remove it from the list)

if i run the job manually it runs absolutely fine with zero issues and the backup appears no problems.

any ideas?

https://www.ads-software.com/extend/plugins/backwpup/