Larger books aren't uploading

I have a webnovel that's really long (2,733 chapters/pages to be exact) and it won't upload. After 15mins It'll get to 69% complete then it crashes my phone and the app. It's an epub file (9.4mb), so thinking that this was the issue I turned it into a pdf (30mb). Sadly, when trying to upload the pdf, after only 2mins it barely gets to 7% before everything crashes. I've uploaded larger books in the past with no issues but now it's becoming a problem. Is there a size or page limit to the app or is this something else entirely that I'm missing? I've tried changing formats, shrinking files, clearing cache, allowing app tracking, deleting and reuploading the files, and even buying a yearly subscription thinking that maybe there were invisible restrictions in place, but nothing seems to fix it. No matter what I do I can't upload this stupid book. I could try splitting the file as a last ditch effort but I'd rather not have to if I can avoid it. Is there anything else I can do? Am I missing something? My other apps can open and read the file so I know it's not corrupted, but for some reason voice aloud just can't do it. Help?