ok, I’ve spent enough time troublehshooting this to be certain:
If the s3 backup settings are incorrect, and enable_s3_backups is true, then a normal rebuild will fail.
I manage the site for a friend who entered his s3 keys incorrectly from day 1 and I’ve never had a problem rebuilding his container before.
An update to discourse/discourse_docker which skips trying to talk to s3, or at least gracefully accepts failure, would mean that people aren’t blindsided by an s3 backup failure during a rebuild