I run backups for a number of sites at 3am every Monday morning. This morning I opened my inbox to far more e-mails from BackWPup than usual.
It appears that for a couple of sites the plugin didn't just run the backup once, but up to fifteen times.
Luckily, whilst resetting the backup job (which I had to do because the update deleted the S3 credentials!!!) I had changed the name of the backup. Otherwise, I would have lost the 4 weeks worth of backups that I have as they'd have been overwritten by the 15 that were performed this morning!