First, I'd like to say how much I love the Calibre software! Its so nice to have the freedom to buy books elsewhere and convert them easily for my kindle

I do have a question - and I apologize if this has already been asked but I couldn't find it elsewhere in the forum.
I recently bought a book series and was able to convert five of the books successfully however two of them get stuck at 67% completed. Books 1-4 and book 7 converted great but books 5 & 6 won't finish no matter how long i wait.
I have downloaded the most recent calibre update, removed and reuploaded the books to calibre and let it spin for five hours to see if it was just wait time. I think the problem is in the books themselves not calibre - its the only thing that makes sense to me - but if you have any suggestions, I would greatly appreciate it.
Thanks!