Reviewing the support case, it seems the file was corrupted or format changed as it moved thru the SFTP.
For anyone reading this and seeking help, here are recommended steps to help locate the point-of-failure.
Manually download and unzip / decompress the file , at each place it travels through.
In this case, it would be download from blob and unzip, download from SFTP and unzip. If either fails, then you know the file is not in the correct format at that location. If both succeed, yet Data Factory fails, then it may be an issue with Data Factory. Please let us know if the last one is the case.