Every time I write up my author's notes post for a new page, the site only keeps the first couple lines, and deletes the rest. This started a couple weeks ago. It's the same when I try to go in afterwards and edit the notes. Anything past the first few lines just ceases to exist. Is there some brand new character limit that I'm not aware of?

Nope. I've just tested this and there shouldn't be an issue.

Are you using special characters in your text? Things like these: > <

The page sees those as HTML tags and makes a cut off point after them.

Yes, whenever we've seen that issue it's because someone is putting in s