Hi Rowan-
Thanks for reaching out! I’m sorry to hear about the 404 error on your older posts.
I checked out your site, and it looks like you’ve already solved this. When I go to Page 2 of your Events category, I see a post from September 2019 show up first, going back to Page 3 I see posts starting from November 2018.
Did you already figure this out, and if so, do you mind sharing how you resolved it for anyone else who mind find this topic in the future?