I had a couple of short story collections from Audible that would begin stuttering or that would just cut out after a certain point. I sent in a problem report to audible and they sent me a response that all Apple devices up to and including the newest iOS devices have a limitation of file size with audio tracks, the problem I had was caused by encountering this limit. All Audible books longer than a certain time, something like 24 hours in Enhanced format will have this problem. Apple and audible are aware of the problem and Apple seems to have no real interest in fixing it. Audible suggests that one set the Audible library page to split the book up into sections, in fact they suggest dropping from the highest quality audio format to a lower quality format because getting Enhanced quality books to show download links for the divided versions of the books is inaccessible with most screen readers and the lower quality audio formats automatically show up as split books.
I find this really annoying as I have a very distinct preference for books as a single file and I spent a very long time redownloading my library when Enhanced format was introduced so I could have my library stored locally, with undivided books all with the metadata edited by me to make sure all of the books show up in proper order within a series instead of being scattered about listed alphabetically by title.
I could get sighted help to redownload the Enhanced books that are split after figuring out which books will be affected by this problem and then re-edit the metadata yet again for these books, but I really wish Apple would just fix this problem. I know that this problem doesn't have to exist as other manufacturers do not have it. How difficult it would be to fix, I don't know, but Apple has to decide it is worth their while to look into it before we can find out. I am hoping that forum members might consider taking a moment to go to Apple's feedback page and send a bug report about this issue. I know that there are others bothered by this, even some sighted users as I found a few topics on various Apple related forums, but the more Apple hears about the issue, the more likely they are to give it some attention.