Audiobook only showing half of the total time in the music app

I have recently got a new book that has 4 parts each are 6-7 hours long, but when I open them on my iphone in the music app it only shows the slider half the time it should. Example the first part shows as 7:52:00 before I begin it, but when I start it the slider changes to 0:00 to 4:30:00. The file will play and will play past 4:30:00, but if I stop playing it, it moves on the next section. I have tried used other app such as bookmobile, but it stops playing in the same place. The files work fine in iTunes and shows the correct times. I have changed the media kind to Audiobook and I have remember playback position checked in iTunes. This has only started in the last 2-3 books that I have put on my phone, I have listened to many audiobooks before this issue started.