During this year, Google is upgrading automatically older spreadsheets to the new version of Google Sheets, and in my case this upgrading process is generating duplicated (or triplicated!!!) sheets.
I think Insync is producing this duplication of files.
@vsuarez I understand how frustrating this is for you. We have to investigate what causing your issue. Please send your logs.db and out.txt file to support@insynchq.com.