Re: WINSCP SYNCHRONIZE COMMAND - DATA LOSS
Please read FAQ, if it does not help, come back.
https://winscp.net/eng/docs/faq_transfer_size_change
https://winscp.net/eng/docs/faq_transfer_size_change
Before posting, please read how to report bug or request support effectively.
Bug reports without an attached log file are usually useless.