Got a download error of "Error: Unable to save resume file: File name too long". When downloading a magnet using Transmission. I tried to fix it by downloading the torrent and changing the filename of the torrent but that did not work.
Although I fixed it myself I wanted to share this as there are many workarounds including using other programs like deluge or rtorrent, trying to edit the filename, or downloading something called the long filename tool.
None of those work if your download folder is in your encrypted home folder.
For me it turns out it came down to the download folder path which was in my encrypted 'home' folder. Changing the filepath fixed the error.
To change the download location in Transmission:
Edit>Preferences>Downloading, and then clicking on the drop down box to the right of "save to location" is how to change the folder path.