Downloading UTF-8 filenames from an FTP-server that does not support them, with System.Net.FtpWebRequest

I have written a windows service in .Net that monitors an FTP location for new files, which it then downloads to a local folder for processing. To be precise, the tool first renames the file before downloading it. It uses the .Net standard FtpWebRequest class from System.Net. Every once in a while, a file could not be downloaded, and the FtpResponse would be 550 – Action not taken, file unavailable. This happened especially if the file name had “special characters” in it, one example being a file named ANDRÉ.XML. The workaround was simple: I’d launch an FTP application, rename the file to ANDRE.XML, and it would quickly be picked up by my tool again.

It bothered me that somehow the FTP application was able to rename the file, while FtpWebRequest was not. (It also bothered me that every once in a while I had to fix a stuck file like this, but let’s not go down that road here.) So I attached a trace log to see what was going on.
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