Howdy Keidrych,
Thanks for running through those troubleshooting steps and creating a new topic. I am as puzzled as you are. We never see 404 errors in the default setup. I have a few idea on things we can try.
This post outlines a few steps on how to fix 404 errors, mind running through them? If that does not fix it, you might try disabling then reenabling all of our plugins. Again, if that did not fix it, please try going to Settings > Permalinks and clicking save again. If that does not help, would you mind pasting this snippet into your theme’s functions.php, and adding a test event during the next month? That snippet will add a little bit of debugging info your theme’s source view for me to look at. If you get to this step and nothing has fixed it, please let me know once this snippet is in place and I will take a look at it. Thanks!
Let me know if you have any questions.
– Brook