I recently upgraded from 5.0.3 to 5.1.3 and some imports (from AWS) don't work anymore.
I wasn't able to determine what creates the issue exactly. My files contain one JSON object per line, all with proper formatting. It's unclear but it seems to work better if I download one of the file and import it this way, whereas imports from AWS fail (including imports that worked prior to the update).
I'm downgrading with the back-up to check if DSS is the issue.