(S)FTP Error: "Meet authentication failure when connect to Sftp server"

Every so often when running an Azure Data Faxtory pipeline in which we attempt to source multiple files from an SFTP Server and subsequently dump them in a blob storage, we'd run into the following error:

After a lot of poking around and testing, we determined this error is caused by the amount of connections we are allowed to simultaneously open up on the (third party) SFTP Server.

This has been escalated to Microsoft, as the erorr message is confusing; after all, it points to the sink, which in our case is the Blob storage.

You can have a look at the thread on MSDN to follow progress on the issue.