S3 backup error "An error occurred () when calling the PutObject operation"

Recently my S3 backups (to Scaleway), which had been working fine, started throwing this error:

Attempt of put Nr. 1 failed. S3UploadFailedError: Failed to upload /tmp/duplicity-qtz2gmjw-tempdir/mktemp-0vovvmd9-3 to my-backup/mail/duplicity-inc.20240306T035509Z.to.20240307T035509Z.vol1.difftar.gpg: An error occurred () when calling the PutObject operation:

That’s all there is, no further explanation. When I look at the bucket, the backups all appear to be there, so I don’t know what this error means.

Any idea what may be wrong, or how I can get better error message?

I had similar here, symptom was the same as yours:
https://discourse.mailinabox.email/t/aws-s3-policy-blocking-duplicity-restore-solved/10216/2

Cause was a malformed URI