CircleCI deploy looks successful, but exits with code 1? - amazon-s3

Question

I have a circleci configuration that runs a script to deploy a storybook site. It's essentially cding into my frontend monorepo packages, running yarn install, builds the storybook and syncs it to an S3 bucket.
(redacting a few things like names of packages and files)
It starts a with job within my circle's config file:
deploy-package-storybook:
<<: *defaults
working_directory: ~/root
steps:
- checkout
- <<: *install_aws
- attach_workspace:
at: ~/
- run:
name: Deploy Storybook
command: |
~/root/bin/deploy-storybook.sh PACKAGE
The script looks like this:
echo "${CYAN}deploying storybook\n"
cd packages/${TAG}
yarn build-storybook
aws s3 sync ./artifacts/storybook s3://storybook.website.us/${TAG} --delete || slack_alert storybook-deploy-fail
slack_alert "deploy-storybook-success"
When it runs in Circle, it seemingly finishes syncing and even sends a slack alert to my channel that it successfully deploys, but however at the end of it, it shows this:
upload: artifacts/storybook/vendors~main.8c562e1c344f6a5f2073.bundle.js to s3://storybook.website.us/package/vendors~main.8c562e1c344f6a5f2073.bundle.js
0
ok
Exited with code exit status 1
CircleCI received exit code 1
However I'm not entirely sure why it does this. It's successfully synced, so it should pass, right?
Things I've done:
I've tried adding a --debug flag to aws s3 sync like so:
aws s3 sync ./artifacts/storybook s3://storybook.website.us/${TAG} --delete --debug
and it returns with something like this:
2020-03-16 13:14:28,349 - ThreadPoolExecutor-0_2 - botocore.hooks - DEBUG - Event needs-retry.s3.PutObject: calling handler <botocore.retryhandler.RetryHandler object at 0x7fcc35212dd0>
2020-03-16 13:14:28,349 - ThreadPoolExecutor-0_2 - botocore.retryhandler - DEBUG - No retry needed.
2020-03-16 13:14:28,350 - ThreadPoolExecutor-0_2 - botocore.hooks - DEBUG - Event needs-retry.s3.PutObject: calling handler <bound method S3RegionRedirector.redirect_from_error of <botocore.utils.S3RegionRedirector object at 0x7fcc35212e10>>
2020-03-16 13:14:28,350 - ThreadPoolExecutor-0_2 - botocore.hooks - DEBUG - Event after-call.s3.PutObject: calling handler <function enhance_error_msg at 0x7fcc35c79320>
2020-03-16 13:14:28,350 - ThreadPoolExecutor-0_2 - s3transfer.utils - DEBUG - Releasing acquire 34/None
upload: artifacts/storybook/vendors~main.5f43fbfd82bbe3ed3177.bundle.js to s3://storybook.website.us/package/vendors~main.5f43fbfd82bbe3ed3177.bundle.js
2020-03-16 13:14:28,365 - Thread-1 - awscli.customizations.s3.results - DEBUG - Shutdown request received in result processing thread, shutting down result thread.
0
ok
Exited with code exit status 1
CircleCI received exit code 1
This isn't my area of expertise, so I'm really lost on what to do with errors like these. Could someone please help?