In an Amazon AppFlow sync between S3 and Salesforce, how can I resolve a vague error that processing failed "with message: null"?

Question

Starting last week, an Amazon AppFlow flow I have to sync CSVs from S3 to Salesforce Accounts has been failing with this vague error:

Found a part that failed processing 2021-03-15T16:00:05.581Z with message: null

There are no further details in the S3 folder for transfer errors, or in our CloudWatch events. (We have both enabled.) In addition, it looks like someone is experiencing the same problem in this AWS Forum thread. I've added some additional details in there, too.

I've tried reducing the number of rows in the sync, editing the flow, and even recreating it. But it still persists.

Answer 1

This error was happening because it was failing a Validation where the action was "Terminate Flow" (rather than ignore the offending row).

AWS support acknowledged that the error message is unclear and is working on a fix.

For now, the workaround is to fix the underlying data issue that is causing the validation rule to fail.