Ethan I don't know how the system works behind the scenes, but for my particular niche (pianos and keyboard musical instruments) I can see some types of "incorrect" post which might be occurring.
1. Completely (seemingly) off-the-wall suggestions such as the label maker, gym equipment etc.
These appear to be unrelated to anything I've ever written about or my audience would find interesting (or at least, expect to find on my site).
2. Suggestions related to a relevant company but an irrelevant product
Yamaha makes digital pianos and music keyboards but it also makes other types of musical instrument, as well as motorcycles and lots of other items.
Casio makes digital pianos and music keyboards but it also makes calculators and watches.
These would need some extra context matching.
3. Suggestions which are broadly topical on music but not niche enough.
This includes the 'guitar' posts which I suspect are coming up because they are related in the music sphere. I've only mentioned the guitar maybe two or three times in the site's history and it's not a major part of it.
In fact #1 posts are the ones which had started creeping in and may have been related to the bug you mentioned. #3 is very common, with #2 somewhere in between.