Yup, looks like a bug.
You can try removing the “File name” variable before selecting the FTP file, but I don’t think this is the issue.
Hope this helps! Let me know if there are any further questions or issues.
— @samliew
P.S.: Did you know, the concepts of about 70% of questions asked on this forum are already covered in the Make Academy. Investing some effort into it will save you lots of time and frustration using Make later!