I am having the same issue. It may have to do with the update from Kindle. I have seen in other areas, mainly the reviews from Kindle on the App Store, that this is happening due to a Page Flip function, of some sort.
To me, it seems that the game is up. I thought it was only a matter of time until both sides of the aisle realized that they were losing out on Audible downloads for visually impaired reading of Amazon material and iBooks in order to have the speak screen function for Apple material. I don't want to buy iBooks when I have my entire library in Kindle, but if allows me to listen to books, then oh, well - Amazon is losing out.
Seems like a turf war/money battle to me which is SO WRONG for people that actually need the "speak the screen" function for listening to books. Highly unethical, in my opinion. Perhaps they can work it out?
A fix would be needed where the speak function, which works fine in other apps, to work properly in Kindle. May be a bug, but part of me thinks the above mentioned shoe has dropped. It seemed too good, all along, to be able to have the ability to read my book and listen, rather than buy both the book and the audible book.
Any fixes from anyone?