Here’s the other bug.
It looks like Dorico isn’t watching the filesystem for changes and/or hasn’t released the old version of the file file, so even though the old file doesn’t exist on the drive, Dorico is still holding it in memory and then saves it to the old location. (Just guessing.)
Just brainstorming:
I don’t think Dorico should prevent duplicate titles for works, because there are cases where someone might have multiple songs with the same title. (The title is also displayed on the score itself.)
Maybe there could be filename collision detection, and an incrementing number could be added to the ends of filenames to prevent deletion of other pieces with the same titles?
For example, if the file, My Song.dorico, exists, then save the one titled “My Song” as My Song__1.dorico. It could check for __n where n is an integer. The double-underscores would prevent auto-incrementing the version if someone writes a song like “Etude 5” (creating the first file as Etude 5.dorico and the next ones as Etude 5__1.dorico, Etude 5__2.dorico, …). It’s probably rare that people create pieces with titles ending in __<int>.