Looks like my choice of permalinks settings (those prettified urls structures) is causing some issues with older articles. I am aware of the situation and will find a resolution as soon as possible. Apologies for any difficulties you may have accessing older articles on the site in the short term.
UPDATE: With some minor adjustments for more reasonable URLs I think the problem has been resolved. I’ll be reviewing 404s, but if you come across a broken URL that I’ve missed or you need access to immediately, just let me know.