[KevinH]

Unfortunately, Sigil can*not auto fix all broken epubs on import. For those cases, you may want to run a Report and then fix any broken links and things manually. Followed by either FC or epubcheck to verify other epub structures.

In many cases, broken links exist because the underlying file system is not case sensitive and so the urls appear to work for the user on those systems when in fact they are broken. Linux is a nice testing ground for these types of path case issues because it defaults to a case-sensitive file system which makes these types of errors easier to find and fix by a quick visual scan of images in the epub.