Thank you, I really appreciate you looking into this! I have one chapter called "Test Chapter", where I was just trying to see if I could switch to other chapters. I also have one called "In Which Lyre Talks".
I did a few things this morning after you mentioned the zip archive and extraction. When I had first extracted from the Zip, it was in my downloads folder. I tested it, then moved the unzipped folder to my documents. After that, I started having the issue.
So today I deleted the one that existed in documents, moved the zip to documents, and unzipped it there before using it. And now it seems to be working between sessions with no errors!
I'm not a lua person but I do program in C# quite a bit, so I'm wondering if it had just associated the directory with my downloads folder since I ran it / saved a project there first, and couldn't find it once I'd moved it.
Either way, it looks like it's working just fine now! It's not too much of a word loss and I should've saved it in the right spot in the first place. But thank you so much for following up on this one!