Sort by series not putting books of the same series next to each other?

This is an odd one that I haven't seen before.

I've got a lot of books in my collection which are part of series', so my preferred sorting is By Series. I've just added the books from "A Series of Unfortunate Events" to my collection, and now for some reason the books don't all show up next to each other in the sorting.

I've even highlighted all 13 books in the series at the same time, edited the metadata simultaneously for each of them, was sure that the exact phrase "A Series of Unfortunate Events" was entered into the series field, and then applied the change, but it didn't fix the issue.

For some reason, Book 1 of the series is showing up near the beginning of the sort order, as if it starts with the letter "A" (which it, well, does). All 12 of the rest of the books in the series are showing up in the S's section of the sort order, ignoring the word "A" at the start of the name and just sorting it by the second word "Series".

But why is the first book in the series using the first word "A" when it sorts it, but ignoring it for the other 12 books???