Deleting read-only files

We use WinSCP for an automatic file transfer job where it FTPs files to a folder on a remote computer, then deletes the files at the source location. The deletion part fails and exits out though if the file is marked as read-only.

Is there a way to either have WinSCP delete read-only files, or mark all files as non-read-only before the deletion step?

Here's the script:

The delete part fails for read-only files with the error:

System Error. Code: 5. Access is denied

Just run something like this before calling WinSCP:
https://superuser.com/q/653951/213663