Can't access (some) old posts

My WordPress install is being inconsistent about access to (really) old posts. For example, if I try to access post 90 (splowey.com/?p=90), I get a page not found. However, this post does show up in my archive search results (it’s the first post at the top of this archive page – https://splowey.com/2004/10/) and I can access the text of the post through my admin panels, where it is clearly marked as “public”, so it’s definitely there and in the database and with the right access setting. It is not a permalink problem since permalinks are generally working on my blog and the same issue occurs whether I access the problem posts their permalinks or via splowey.com/?p=(whatever the page ID is).

Any suggestions on how to fix this/what to look at to nail down the problem? It seems like I’m seeing this problem on posts with page IDs less than 100, though there are some posts with low ID numbers that load just fine.

Thanks!