@michael it's a known issue but kinda tricky to solve after recent changes to a dependency code.
You could try the workarounds listed here and see if they work.
:github: https://github.com/mastodon/mastodon/issues/33624
I'm also using B2 but not having trouble with Sidekiq due to these workarounds.
Here's my .env.prod:
```
S3_REGION=eu-central-000
S3_ENABLED=true
S3_PROTOCOL=https
S3_BUCKET=xyzxyz
S3_READ_TIMEOUT=15
S3_OPEN_TIMEOUT=15
S3_RETRY_LIMIT=3
S3_ALIAS_HOST=i.cdn.bolha.one
S3_FORCE_SINGLE_REQUEST=true
S3_DISABLE_CHECKSUM_MODE=true
S3_ENDPOINT=https://s3.eu-central-000.backblazeb2.com
AWS_ACCESS_KEY_ID=xyzxyz
AWS_SECRET_ACCESS_KEY=xyzxyz
S3_PERMISSION=
```