I stumbled upon it on a communications glitch. See “Unexpected difference in fileset” errors [2.0.3.9], and what I had to say. Did you happen to test it to a local file? If “Stop” can get it there, it’s an easier test to run. Still, your test is easier than where I left off, which involved cutting off the communications at the server…
Thanks for helping track it down. Getting a good reproducible test case is (IMO) key to understanding and fix. Yours actually looks good enough to file as an issue where the development team might start working. Would you be able to file? In addition to attracting developers, issues get tracked better than posts here…