Preventing Dropbox from (re)creating Iconr folders

I’m trying to migrate away from Dropbox to Syncthing. In the process, I’ve hit a small snag. It seems that, in my Dropbox folder, two of the folders contain a file called Iconr where r is, bizarrely, the carriage return character. Problem is, this is invalid on Windows, so Syncthing is failing here.

I’ve tried the usual tricks of stopping Dropbox and deleting this file. However, as soon as I start Dropbox sync again, this file is re-created. Curiously enough, Dropbox itself filters out this file during synchronization, meaning it’s not visible in Dropbox’s own file listings and does not appear on other devices.

Would appreciate ideas on what this is and how to get rid of it permanently.