There seem to be situations where this creates problems in the EPUB export. Here’s my situation when I’m creating print and epub versions of books.
1. There’s a folder with tifs of the images for the print version. I link to that folder and they export to PDF without a hitch.
2. There’s another folder with similarly named jpgs of those same images. Many of them do NOT export to the EPUB if Use Original Image is checked. According to the description above, that’s because ID isn’t using the rasterised image but somehow cannot find the original. This seems to happen when the original is changed.
I’ve not been able to find any work around other that unchecking Use Original Image.
I realize this is probably doing precisely what it was intended to do, but for many users it no only looks like a bug, because User Original Image defaults to checked, they won’t be able to figure out what those images in the ID document are not appearing in the epub output.