I saw this error on a few
DataLoadUploadLog entries after the upgrade to 7.7. It took me a while to figure out the reason for this error and decided to share it here:
It turns out that the issue was that I had not set
contentEncoding properly on the files in S3.
SourceFile.fetch() on the file reflected its size but the number of rows was 0 and contentEncoding property was not set.