Comment 2 for bug 2029521

Hmm, I tried creating bookmarks in that book on my mac and they all
worked. The bookmarks you created somehow have no position information
in them. I will change calibre in the next release to at least show an
error when this happens rather than creating a non-functioning bookmark.
However, without a way to reproduce the creation of the non-functioning
bookmarks I cant actually fix the problem. Have you changed any viewer
settings from defaults?