Exported Book broken Hyperlinks

I have created hyperlinks in my book, a cookbook, referencing bookmarks to other recipes in my cookbook. This makes it easy to move from a recipe to a dry rub recipe and back again. The links work perfectly when I use them in iBook Author but when I export to iBook format they no longer function. Has anybody else had this issue and is there a fix?

iBooks Author 2.4

OSX El Capitan

iOS 9.02

Thanks,

Brian