Error : Azure Storage - SFTP(preview)

We are using Azure Storage - SFTP(preview) service to upload files to Azure Blob Containers, We are able to upload multiple files simultaneously using the SFTP client. But we are experiencing inconsistency in transferring files to SFTP account as some of these files are failing - we are getting ‘Invalid block size’ error from Azure blob storage.

Please let us know what may be causing these issue as we have to manually copy/reinitiate upload to SFTP for the failed files.