[KevinH]

Sorry, but because Sigil must run on case insensitive file systems and adding files can come from any external path (ie only the filename itself is valid/unique when selecting an external file) duplicate names (even if case sensitively unique) must be changed to allow the add or move to happen. Otherwise with image files it will prompt you to overwrite them.

Once the file's full bookpath is unique, you can rename it back to what you want.

I typically rename the problem file to some unrelated temp name first to prevent issues.

Yes that can be a pain in the ass but occurs rarely enough I have not fought the code to try and change it.