[Vaesse]

I figured my issue out (kind of) after sleeping on it. Turns out I was looking at it backwards (I rarely look at the device through Calibre unless something has gone wrong). The books that were showing the series info in Calibre were the bugged ones, the ones with just author and title were fine on my Kindle. Removing and readding those solved the problem.

I would love to figure out how it gets bugged and avoid that for the future, but at least I found a solution (even if it's not ideal, because I lose me place in all the bugged books, and I'm usually in the middle of quite a few books).