I noticed that when I uploaded a over-limit .docx file that can't be converted into Google Doc into Google Drive, Syndocs appears to retry several times on and on (I tested at least 3 times) and won't stop it or put it on the error log.
Official limit : "Documents: Up to 1.02 million characters. If you convert a text document to Google Docs format, it can be up to 50 MB." https://support.google.com/drive/answer/37603?hl=en
Example: .docx file of 20MB but containing more than 2 Millions characters.
Note: If I upload the file manually (drag and drop) directly into Google Drive. I receive an error and I can "retry". It does not says that is it off-1Million characters limit !