It was time change yesterday (November 1), and when it was done, our progressive backups stopped working! We got emails saying that it couldn't rename the progressive backup folder (error #795). I had to disable and enable the progressive backup option to get it back to work again.
FileMaker Server 13v9 on Windows Server 2012 R2. I saw to update to 13v10, but I didn't see anything about that problem in the release notes, so I didn't apply the update.