I've been getting them lately as well. But it seemed to start around the time I switched to Transmission GUI 5.01 (Windows) a couple of weeks ago. But since the torrent continues to download and upload, it really wasn't an issue.
Currently, I'm seeing it on "KeptSecretXXX - Drug Bust". So, if that file was reported as a dupe, then I guess we're the same page of "non-issue", which just leave the question of "'Why am I still here and not wankin'?" (The question of a lifetime.)