There is a use case where due to the way insync sync with google drive a duplicates are being created.
The issue will be gone if Insync convert .odf files created localy to google's format before uploading as requested here: https://forums.insynchq.com/t/automatically-convert-new-docs-to-google-format/2719/5
Anyway, the steps to reproduce the bug:
1. Enable conversion of google docs, spreadsheets etc.. to desktop format (.ods)
2. Create a .ods spreadsheet and save it locally
3. Wait for the document to be uploaded to google drive
4. Open google drive, double click the document and edit it using google's spreadsheet
Now there are two copies of the same document.
First one is the original .odf created locally, and second one is the one that google created when executing step 4.
But if we convert the .odf document to googles format before uploading there wont be an issue.