Every so often, after clicking around the site a bit, when I click back to Characters or Campaigns from the "My Content" section, it'll show me somebody else's characters or campaigns. Logging out or logging in solves the problem, or clicking around a little bit more and then returning to those pages, but it does keep happening.

It's happening to me too, I'm getting cached results in the "My Characters" option. Empty results or not my characters

Happening to me too. Trying to do a PbP but trying to see other people's characters made on this site resulted in 404 error, same with my campaign invite to said players.

Same here.  Only occasionally.