klaus knechtel

I found a solution for my experience with this bug. I had to go to  the following path:

...AppData\Local\Packages\Microsoft.MinecraftUWP_[ID String]\LocalState\games\com.mojang\resource_packs

and delete any folders with (1) in the folder name, and one folder representing a pack that wouldn't even show up in the list of options when I opened My Packs while in a realm. Once I relaunched a couple times suddenly I had access to My Packs again. Hope this helps! 

I'm assuming that one was causing the primary issue, and had a bad .JSON like @Mike Shultz proposed.

Since all the linebreak-related issues seem to be getting funneled to this tracker, I will add what I have observed about book and quills on a Realm.

When attempting to make a bulleted list in a book and quill, I encountered an issue whereupon any text on an EVEN numbered page would lose its linebreaks. Any lists formatted the same on an ODD numbered page would retain that formatting. While editing the book, linebreaks would remain, but the moment I close the book (not sign and close, just exit out of the book and quill interface), and reopen it, text on even numbered pages would have all their text pulled back into a single wrapped line, causing characters that I set to denote the beginning of a new line for readability to wind up in various spots on the page.

And in another book, it was the reverse: ODD pages lost linebreaks while EVEN pages kept theirs. But so far, it was never both at the same time, in any one book and quill. It was either Even broke while Odd worked, or Even worked while Odd broke. So at least there is some sort of pattern there, even if it seems to vary between two versions of the pattern.

https://drive.google.com/drive/folders/1plB3FjuT22moAmYwl3FpTIteYw8lS1p_?usp=sharing

This link is to a folder that contains the WIN10 exports of my realms world saved before 1.18 update, and after (Both mcworlds are well over 50mb), as well as a screenshot with the coordinates I was at when I discovered this bug.
I agree with others that this was probably just an artefact from the world conversion, and it's not like it's an issue per se. Just kinda neat and a probably good indicator of what kind of weirdness can occur when you run world generation again on already loaded chunks.