When uploading a replacement file over an existing image or file property, the new file should be renamed to have the same name. This makes sure that existing links will still work.
This functionality works when a content type does has archiving disabled, but does not when archive is enabled. You can make sure a content type has archiving enabled by extending it in the project and adding `bArchive="true"` as an attribute on the component.
The issue appears to be in the image formtool (core/packages/formtools/image.cfc), `handleFilePost` function. This function moves the old file into the archive folder, then checks for the existence of the old file when naming the new one. Removing the exists check may be the best fix for this.