A bug, and I have absolutely no clue how it happened, since I haven't touched that shop in ages. I can only imagine it's the result of the somewhat janky way I implemented lunatic (and then subsequently un-jankified it), the shop was set to only open for chapter 7. It's fixed for the release later today.
Edit: Just realized what it was. When I did some of the slight reworking of ch. 2 I made a copy of the map to do the changes, in case I wanted to start back from the beginning (SRPG Studio doesn't have great undo functionality for stuff like units), and I deleted the original when I finished. It must have just defaulted to being for the latest map only (since it's by map, not necessarily by chapter).