[Anonomaly]

Thank you guys for your help.
I don't actually use any screenwriting software - I only receive PDFs from writers and they don't always agree or are technically savvy enough to export and send different formats.

But this is interesting! It hadn't occurred to me to open the PDF in Word and then converting the DOCX.
I actually tried that with a different screenplay and uploaded the epub, along with the two samples you both attached, to my device.
For some reason the file that Karellen made looked best on my Kindle, and reacted best to KOReader's styling options. It was also the only file of the three that could change fonts through KOReader, which is significant since I find specific fonts much easier and faster to read.
Could it be because of the removed page numbers and added TOC?
Which settings specifically did you use to do that?

Edit: Bradles is actually right that having page numbers would be more convenient when writing and giving notes, since most writers don't number their scenes until they're almost ready to shoot.
But readability is more important and if I'm right in my guess and the page numbers somehow make the files less compatible then I'd rather remove them and figure out some way to find the right page for a note.