I've further narrowed down the breakage point to between these two items, at least when initially checked (both now fail).
https://news.ycombinator.com/item?id=42937148 (works)
https://news.ycombinator.com/item?id=42937147 (fails)
(Also via email.)
This suggests an item-count or time-based sliding window to me.
As I write this, earliest accessible content is <https://news.ycombinator.com/item?id=42937674> ... and that's just become inaccessible as I'm updating this comment.
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