I accidentally discovered that certain tags weren’t returning all relevant entries on this site. This mostly affected the Gunpla-related content, which is the one type of post that benefits the most from tagging.
It turns out the problem was a bug (or perhaps merely an oversight) in Middleman, in which upper and lower case tags render to the same page, but only one of them counts. A handful of articles with tags like “Gundam” and “Bandai” thus took over those tags. I’ve made everything lowercase, and everything seems to be fine.
I’m glad this was such a quick fix. If not, it might have forced me to seriously consider looking at another static site generator, and I’m really not in the mood to do that right now.