I looked into our code and it behaves correctly on our end. It seems like a bug in Dropbox, it keeps telling me that the file exists and it asks me whether I want to replace it or keep both, although I definitely have no file in target directory. On other attempt it indeed saved the same file twice (without asking to override etc). Then, after I changed the name of a file being saved, it stopped misbehaving. When reading customer reviews on AppStore, there are tons of reports that it is buggy, so at this point I’d blame Dropbox. I tried with 72.2.2 first, then I updated to 78.2.2 and it can still go wrong.