I sideloaded the book several months ago. I don't recall if I had deleted it or if it broke first, but I have tried deleting it from on the device and it deletes properly only to return after it wakes up. The books shows up as a normal, sideloaded epub sans cover. I have no idea why it continues to show up; I have no record of it in my purchase history, or online Kobo library and it doesn't show up in Kobo Desktop so I'm fairly certain the problem is confined to the reader.
I don't have any SQL knowledge, though I did try poking around in the database once before deciding that wasn't a very smart idea (I didn't change anything).
Changing the fonts do allow the text to show, but only briefly; it quickly disappears again as soon as the menu closes.