Re: Can't create .filepart with a file that has no extension.
Please attach a full session log file showing a successful download of a file with an extension and failed download of a file from the same remote folder to the same local folder without an extension.
To generate the session log file, use
/log=C:\path\to\winscp.log command-line argument. Submit the log with your post as an attachment. Note that passwords and passphrases not stored in the log. You may want to remove other data you consider sensitive though, such as host names, IP addresses, account names or file names (unless they are relevant to the problem). If you do not want to post the log publicly, you can mark the attachment as private.