An error when overwriting remote files

I have a directory that is owned by root:root and has a 757 permission. I login using kaysho:whatever to winscp and I can copy a file from local dir to remote dir normally, but when the file is already in the remote dir and I try to overwrite it, I receive (attached)

what could be wrong ?

Thanks

Please read FAQ:
https://winscp.net/eng/docs/faq_not_owner