Error 521 "Can't create directory" when uploading file edited locally (ONLY in a remote subfolder)

[davidefleurs]

In some specific FTP servers (not in every server), when I edit a file in a subfolder ftp-remote-edit send the error "521: Cant' create directory" and fail to upload the file when i save it (and commit modifications to the file).
FTP access is working correctly and there are no access limitation to the subfolders: the problem occurs in every subfolder but not in the root folder (/).
Same issue occurs on creating a new file in subfolders.
This start happening only few month ago.